diff --git a/google_sign_in_dart/README.md b/google_sign_in_dart/README.md
index c8e9a8db..97174772 100644
--- a/google_sign_in_dart/README.md
+++ b/google_sign_in_dart/README.md
@@ -17,24 +17,19 @@ mainly used on Desktop.
 1. Run `flutter pub get`
 1. Import
     ```dart
-    import 'package:google_sign_in/google_sign_in.dart';
     import 'package:google_sign_in_dartio/google_sign_in_dartio.dart';
     ```        
 1. Register the package
-    ```dart 
-    import 'package:flutter/material.dart';
-    import 'package:google_sign_in/google_sign_in.dart';
-    import 'package:google_sign_in_dartio/google_sign_in_dartio.dart';
-    
-    void main() {
+    ```dart
+    Future<void> main() async {
       if (isDesktop) {
-        GoogleSignInPlatform.register(clientId: <clientId>);
+        await GoogleSignInDart.register(clientId: <clientId>);
       }
     
       runApp(MyApp());
     }
     ``` 
-    Note: You might want to `await` for the `register` method to finish before calling any `GoogleSignIn` methods when your app starts.  
+    Note: You should ensure the `register` method completes before calling any `GoogleSignIn` methods when your app starts. 
 
 ###  Usage
 You can use the normal `GoogleSignIn` methods.
@@ -54,12 +49,11 @@ keep the user logged in, you need to deploy a oAuth code exchange endpoint. Once
 the package like this. 
 
     import 'package:flutter/material.dart';
-    import 'package:google_sign_in/google_sign_in.dart';
     import 'package:google_sign_in_dartio/google_sign_in_dartio.dart';
     
-    void main() {
+    Future<void> main() async {
       if (isDesktop) {
-        GoogleSignInPlatform.register(
+        await GoogleSignInDart.register(
             clientId: <clientId>, 
             exchangeEndpoint: <endpoint>,
         );
diff --git a/google_sign_in_dart/example/lib/main.dart b/google_sign_in_dart/example/lib/main.dart
index 3d476480..88a98ae3 100755
--- a/google_sign_in_dart/example/lib/main.dart
+++ b/google_sign_in_dart/example/lib/main.dart
@@ -5,22 +5,25 @@
 // ignore_for_file: public_member_api_docs
 
 import 'dart:async';
-import 'dart:convert';
 
+import 'package:collection/collection.dart' show IterableExtension;
 import 'package:extension_google_sign_in_as_googleapis_auth/extension_google_sign_in_as_googleapis_auth.dart';
 import 'package:flutter/foundation.dart';
-import 'package:html_unescape/html_unescape.dart';
 import 'package:flutter/material.dart';
 import 'package:google_sign_in/google_sign_in.dart';
 import 'package:google_sign_in_dartio/google_sign_in_dartio.dart';
 import 'package:googleapis/gmail/v1.dart';
 import 'package:googleapis/people/v1.dart';
-import 'package:googleapis_auth/auth.dart';
+import 'package:googleapis_auth/googleapis_auth.dart';
+import 'package:html_unescape/html_unescape.dart';
 
 import 'platform_js.dart' if (dart.library.io) 'platform_io.dart';
 
-GoogleSignIn _googleSignIn = GoogleSignIn(
-    scopes: <String>['email', 'profile', PeopleApi.ContactsReadonlyScope]);
+GoogleSignIn _googleSignIn = GoogleSignIn(scopes: <String>[
+  'email',
+  'profile',
+  PeopleServiceApi.contactsReadonlyScope
+]);
 
 Future<void> main() async {
   if (isDesktop) {
@@ -46,11 +49,11 @@ class SignInDemo extends StatefulWidget {
 }
 
 class SignInDemoState extends State<SignInDemo> {
-  StreamSubscription<GoogleSignInAccount> sub;
-  AuthClient _client;
-  GoogleSignInAccount _currentUser;
-  String _contactText;
-  String _emailText;
+  late StreamSubscription<GoogleSignInAccount?> sub;
+  AuthClient? _client;
+  GoogleSignInAccount? _currentUser;
+  String? _contactText;
+  String? _emailText;
 
   @override
   void initState() {
@@ -59,7 +62,7 @@ class SignInDemoState extends State<SignInDemo> {
     _googleSignIn.signInSilently();
   }
 
-  Future<void> _onUserChanged(GoogleSignInAccount account) async {
+  Future<void> _onUserChanged(GoogleSignInAccount? account) async {
     setState(() => _currentUser = account);
     if (_currentUser != null) {
       _client = await _googleSignIn.authenticatedClient();
@@ -70,27 +73,26 @@ class SignInDemoState extends State<SignInDemo> {
   Future<void> _handleGetContact() async {
     setState(() => _contactText = 'Loading contact info...');
 
-    final PeopleConnectionsResourceApi connectionsApi =
-        PeopleApi(_client).people.connections;
+    final PeopleConnectionsResource connectionsApi =
+        PeopleServiceApi(_client!).people.connections;
 
     final ListConnectionsResponse listResult = await connectionsApi.list(
       'people/me',
       requestMask_includeField: 'person.names',
     );
 
-    String contact;
-    final List<Person> connections = listResult.connections;
+    String? contact;
+    final List<Person>? connections = listResult.connections;
     if (connections != null && connections.isNotEmpty) {
       connections.shuffle();
-      final Person person = connections.firstWhere(
+      final Person? person = connections.firstWhereOrNull(
         (Person person) =>
-            person.names.any((Name name) => name.displayName != null),
-        orElse: () => null,
+            person.names!.any((Name name) => name.displayName != null),
       );
 
       if (person != null) {
         final Name name =
-            person.names.firstWhere((Name name) => name.displayName != null);
+            person.names!.firstWhere((Name name) => name.displayName != null);
         contact = name.displayName;
       }
     }
@@ -108,7 +110,7 @@ class SignInDemoState extends State<SignInDemo> {
     setState(() => _emailText = 'Loading emails...');
 
     final bool granted = await _googleSignIn
-        .requestScopes(<String>[GmailApi.GmailReadonlyScope]);
+        .requestScopes(<String>[GmailApi.gmailReadonlyScope]);
 
     if (!granted) {
       setState(() => _emailText = 'Gmail scope was not granted by the user.');
@@ -116,16 +118,15 @@ class SignInDemoState extends State<SignInDemo> {
     }
 
     _client = await _googleSignIn.authenticatedClient();
-    final UsersMessagesResourceApi messagesApi =
-        GmailApi(_client).users.messages;
+    final UsersMessagesResource messagesApi = GmailApi(_client!).users.messages;
 
     final ListMessagesResponse listResult = await messagesApi.list('me');
 
-    String messageSnippet;
-    if (listResult.messages != null && listResult.messages.isNotEmpty) {
-      for (Message message in listResult.messages..shuffle()) {
-        message = await messagesApi.get('me', message.id, format: 'FULL');
-        final String snippet = message.snippet;
+    String? messageSnippet;
+    if (listResult.messages != null && listResult.messages!.isNotEmpty) {
+      for (Message message in listResult.messages!..shuffle()) {
+        message = await messagesApi.get('me', message.id!, format: 'FULL');
+        final String? snippet = message.snippet;
         if (snippet != null && snippet.trim().isNotEmpty) {
           messageSnippet = HtmlUnescape().convert(snippet);
           break;
@@ -176,7 +177,7 @@ class SignInDemoState extends State<SignInDemo> {
                 children: <Widget>[
                   const Text('You are not currently signed in.'),
                   const SizedBox(height: 16.0),
-                  RaisedButton(
+                  ElevatedButton(
                     onPressed: _handleSignIn,
                     child: const Text('SIGN IN'),
                   ),
@@ -190,21 +191,21 @@ class SignInDemoState extends State<SignInDemo> {
               ListTile(
                 leading: kIsWeb
                     ? GoogleUserCircleAvatar(
-                        identity: _currentUser,
+                        identity: _currentUser!,
                       )
                     : ClipOval(
                         child: Image.network(
-                          _currentUser.photoUrl ??
+                          _currentUser!.photoUrl ??
                               'https://lh3.googleusercontent.com/a/default-user=s160-c',
                         ),
                       ),
-                title: Text(_currentUser.displayName ?? ''),
-                subtitle: Text(_currentUser.email ?? ''),
+                title: Text(_currentUser!.displayName ?? ''),
+                subtitle: Text(_currentUser!.email),
               ),
               if (_contactText != null)
                 ListTile(
                   title: Text(
-                    _contactText,
+                    _contactText!,
                     maxLines: 1,
                     overflow: TextOverflow.ellipsis,
                   ),
@@ -213,7 +214,7 @@ class SignInDemoState extends State<SignInDemo> {
               if (_emailText != null)
                 ListTile(
                   title: Text(
-                    _emailText,
+                    _emailText!,
                     maxLines: 1,
                     overflow: TextOverflow.ellipsis,
                   ),
@@ -221,18 +222,18 @@ class SignInDemoState extends State<SignInDemo> {
                 ),
               ButtonBar(
                 children: <Widget>[
-                  FlatButton(
+                  TextButton(
                     onPressed: _handleSignOut,
                     child: const Text('SIGN OUT'),
                   ),
-                  FlatButton(
+                  TextButton(
                     onPressed: () {
                       _handleGetContact();
                       _handleGetEmail();
                     },
                     child: const Text('REFRESH'),
                   ),
-                  FlatButton(
+                  TextButton(
                     onPressed: _handleGetEmail,
                     child: const Text('ADD GMAIL SCOPE'),
                   ),
diff --git a/google_sign_in_dart/example/macos/Podfile b/google_sign_in_dart/example/macos/Podfile
index d60ec710..dade8dfa 100644
--- a/google_sign_in_dart/example/macos/Podfile
+++ b/google_sign_in_dart/example/macos/Podfile
@@ -9,74 +9,32 @@ project 'Runner', {
   'Release' => :release,
 }
 
-def parse_KV_file(file, separator='=')
-  file_abs_path = File.expand_path(file)
-  if !File.exists? file_abs_path
-    return [];
+def flutter_root
+  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'ephemeral', 'Flutter-Generated.xcconfig'), __FILE__)
+  unless File.exist?(generated_xcode_build_settings_path)
+    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure \"flutter pub get\" is executed first"
   end
-  pods_ary = []
-  skip_line_start_symbols = ["#", "/"]
-  File.foreach(file_abs_path) { |line|
-      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
-      plugin = line.split(pattern=separator)
-      if plugin.length == 2
-        podname = plugin[0].strip()
-        path = plugin[1].strip()
-        podpath = File.expand_path("#{path}", file_abs_path)
-        pods_ary.push({:name => podname, :path => podpath});
-      else
-        puts "Invalid plugin specification: #{line}"
-      end
-  }
-  return pods_ary
-end
 
-def pubspec_supports_macos(file)
-  file_abs_path = File.expand_path(file)
-  if !File.exists? file_abs_path
-    return false;
+  File.foreach(generated_xcode_build_settings_path) do |line|
+    matches = line.match(/FLUTTER_ROOT\=(.*)/)
+    return matches[1].strip if matches
   end
-  File.foreach(file_abs_path) { |line|
-    return true if line =~ /^\s*macos:/
-  }
-  return false
+  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Flutter-Generated.xcconfig, then run \"flutter pub get\""
 end
 
+require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
+
+flutter_macos_podfile_setup
+
 target 'Runner' do
   use_frameworks!
   use_modular_headers!
 
-  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
-  # referring to absolute paths on developers' machines.
-  ephemeral_dir = File.join('Flutter', 'ephemeral')
-  symlink_dir = File.join(ephemeral_dir, '.symlinks')
-  symlink_plugins_dir = File.join(symlink_dir, 'plugins')
-  system("rm -rf #{symlink_dir}")
-  system("mkdir -p #{symlink_plugins_dir}")
+  flutter_install_all_macos_pods File.dirname(File.realpath(__FILE__))
+end
 
-  # Flutter Pods
-  generated_xcconfig = parse_KV_file(File.join(ephemeral_dir, 'Flutter-Generated.xcconfig'))
-  if generated_xcconfig.empty?
-    puts "Flutter-Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
+post_install do |installer|
+  installer.pods_project.targets.each do |target|
+    flutter_additional_macos_build_settings(target)
   end
-  generated_xcconfig.map { |p|
-    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
-      symlink = File.join(symlink_dir, 'flutter')
-      File.symlink(File.dirname(p[:path]), symlink)
-      pod 'FlutterMacOS', :path => File.join(symlink, File.basename(p[:path]))
-    end
-  }
-
-  # Plugin Pods
-  plugin_pods = parse_KV_file('../.flutter-plugins')
-  plugin_pods.map { |p|
-    symlink = File.join(symlink_plugins_dir, p[:name])
-    File.symlink(p[:path], symlink)
-    if pubspec_supports_macos(File.join(symlink, 'pubspec.yaml'))
-      pod p[:name], :path => File.join(symlink, 'macos')
-    end
-  }
 end
-
-# Prevent Cocoapods from embedding a second Flutter framework and causing an error with the new Xcode build system.
-install! 'cocoapods', :disable_input_output_paths => true
diff --git a/google_sign_in_dart/example/macos/Podfile.lock b/google_sign_in_dart/example/macos/Podfile.lock
index edbf2569..99cd80c4 100644
--- a/google_sign_in_dart/example/macos/Podfile.lock
+++ b/google_sign_in_dart/example/macos/Podfile.lock
@@ -1,38 +1,28 @@
 PODS:
   - FlutterMacOS (1.0.0)
-  - shared_preferences (0.0.1)
   - shared_preferences_macos (0.0.1):
     - FlutterMacOS
-  - url_launcher (0.0.1)
   - url_launcher_macos (0.0.1):
     - FlutterMacOS
 
 DEPENDENCIES:
-  - FlutterMacOS (from `Flutter/ephemeral/.symlinks/flutter/darwin-x64`)
-  - shared_preferences (from `Flutter/ephemeral/.symlinks/plugins/shared_preferences/macos`)
+  - FlutterMacOS (from `Flutter/ephemeral`)
   - shared_preferences_macos (from `Flutter/ephemeral/.symlinks/plugins/shared_preferences_macos/macos`)
-  - url_launcher (from `Flutter/ephemeral/.symlinks/plugins/url_launcher/macos`)
   - url_launcher_macos (from `Flutter/ephemeral/.symlinks/plugins/url_launcher_macos/macos`)
 
 EXTERNAL SOURCES:
   FlutterMacOS:
-    :path: Flutter/ephemeral/.symlinks/flutter/darwin-x64
-  shared_preferences:
-    :path: Flutter/ephemeral/.symlinks/plugins/shared_preferences/macos
+    :path: Flutter/ephemeral
   shared_preferences_macos:
     :path: Flutter/ephemeral/.symlinks/plugins/shared_preferences_macos/macos
-  url_launcher:
-    :path: Flutter/ephemeral/.symlinks/plugins/url_launcher/macos
   url_launcher_macos:
     :path: Flutter/ephemeral/.symlinks/plugins/url_launcher_macos/macos
 
 SPEC CHECKSUMS:
-  FlutterMacOS: 15bea8a44d2fa024068daa0140371c020b4b6ff9
-  shared_preferences: 9fec34d1bd906196a4da48fcf6c3ad521cc00b8d
-  shared_preferences_macos: 5e5c2839894accb56b7d23328905b757f2bafaf6
-  url_launcher: af78307ef9bafff91273b34f1c6c0c86a0004fd7
-  url_launcher_macos: 76867a28e24e0b6b98bfd65f157b64108e6d477a
+  FlutterMacOS: 57701585bf7de1b3fc2bb61f6378d73bbdea8424
+  shared_preferences_macos: 480ce071d0666e37cef23fe6c702293a3d21799e
+  url_launcher_macos: 45af3d61de06997666568a7149c1be98b41c95d4
 
-PODFILE CHECKSUM: d8ba9b3e9e93c62c74a660b46c6fcb09f03991a7
+PODFILE CHECKSUM: 6eac6b3292e5142cfc23bdeb71848a40ec51c14c
 
-COCOAPODS: 1.9.3
+COCOAPODS: 1.10.1
diff --git a/google_sign_in_dart/example/macos/Runner.xcodeproj/project.pbxproj b/google_sign_in_dart/example/macos/Runner.xcodeproj/project.pbxproj
index 1f08fe6b..084f7e54 100644
--- a/google_sign_in_dart/example/macos/Runner.xcodeproj/project.pbxproj
+++ b/google_sign_in_dart/example/macos/Runner.xcodeproj/project.pbxproj
@@ -26,11 +26,7 @@
 		33CC10F32044A3C60003C045 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 33CC10F22044A3C60003C045 /* Assets.xcassets */; };
 		33CC10F62044A3C60003C045 /* MainMenu.xib in Resources */ = {isa = PBXBuildFile; fileRef = 33CC10F42044A3C60003C045 /* MainMenu.xib */; };
 		33CC11132044BFA00003C045 /* MainFlutterWindow.swift in Sources */ = {isa = PBXBuildFile; fileRef = 33CC11122044BFA00003C045 /* MainFlutterWindow.swift */; };
-		33D1A10422148B71006C7A3E /* FlutterMacOS.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 33D1A10322148B71006C7A3E /* FlutterMacOS.framework */; };
-		33D1A10522148B93006C7A3E /* FlutterMacOS.framework in Bundle Framework */ = {isa = PBXBuildFile; fileRef = 33D1A10322148B71006C7A3E /* FlutterMacOS.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 		70187420AD7069D6A0D6E273 /* Pods_Runner.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 8FD10AF132D27875663768A9 /* Pods_Runner.framework */; };
-		D73912F022F37F9E000D13A0 /* App.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D73912EF22F37F9E000D13A0 /* App.framework */; };
-		D73912F222F3801D000D13A0 /* App.framework in Bundle Framework */ = {isa = PBXBuildFile; fileRef = D73912EF22F37F9E000D13A0 /* App.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -50,8 +46,6 @@
 			dstPath = "";
 			dstSubfolderSpec = 10;
 			files = (
-				D73912F222F3801D000D13A0 /* App.framework in Bundle Framework */,
-				33D1A10522148B93006C7A3E /* FlutterMacOS.framework in Bundle Framework */,
 			);
 			name = "Bundle Framework";
 			runOnlyForDeploymentPostprocessing = 0;
@@ -71,7 +65,6 @@
 		33CEB47222A05771004F2AC0 /* Flutter-Debug.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Flutter-Debug.xcconfig"; sourceTree = "<group>"; };
 		33CEB47422A05771004F2AC0 /* Flutter-Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Flutter-Release.xcconfig"; sourceTree = "<group>"; };
 		33CEB47722A0578A004F2AC0 /* Flutter-Generated.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = "Flutter-Generated.xcconfig"; path = "ephemeral/Flutter-Generated.xcconfig"; sourceTree = "<group>"; };
-		33D1A10322148B71006C7A3E /* FlutterMacOS.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = FlutterMacOS.framework; path = Flutter/ephemeral/FlutterMacOS.framework; sourceTree = SOURCE_ROOT; };
 		33E51913231747F40026EE4D /* DebugProfile.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = DebugProfile.entitlements; sourceTree = "<group>"; };
 		33E51914231749380026EE4D /* Release.entitlements */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.entitlements; path = Release.entitlements; sourceTree = "<group>"; };
 		33E5194F232828860026EE4D /* AppInfo.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = AppInfo.xcconfig; sourceTree = "<group>"; };
@@ -80,7 +73,6 @@
 		9740EEB21CF90195004384FC /* Debug.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = Debug.xcconfig; sourceTree = "<group>"; };
 		A76B186EF93B9395FA18FCB2 /* Pods-Runner.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.debug.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"; sourceTree = "<group>"; };
 		B6AD4B4FDBD59CE2E1E55422 /* Pods-Runner.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.release.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"; sourceTree = "<group>"; };
-		D73912EF22F37F9E000D13A0 /* App.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = App.framework; path = Flutter/ephemeral/App.framework; sourceTree = SOURCE_ROOT; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -88,8 +80,6 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				D73912F022F37F9E000D13A0 /* App.framework in Frameworks */,
-				33D1A10422148B71006C7A3E /* FlutterMacOS.framework in Frameworks */,
 				70187420AD7069D6A0D6E273 /* Pods_Runner.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -145,8 +135,6 @@
 				33CEB47222A05771004F2AC0 /* Flutter-Debug.xcconfig */,
 				33CEB47422A05771004F2AC0 /* Flutter-Release.xcconfig */,
 				33CEB47722A0578A004F2AC0 /* Flutter-Generated.xcconfig */,
-				D73912EF22F37F9E000D13A0 /* App.framework */,
-				33D1A10322148B71006C7A3E /* FlutterMacOS.framework */,
 			);
 			path = Flutter;
 			sourceTree = "<group>";
@@ -281,7 +269,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "echo \"$PRODUCT_NAME.app\" > \"$PROJECT_DIR\"/Flutter/ephemeral/.app_filename\n";
+			shellScript = "echo \"$PRODUCT_NAME.app\" > \"$PROJECT_DIR\"/Flutter/ephemeral/.app_filename && \"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh embed\n";
 		};
 		33CC111E2044C6BF0003C045 /* ShellScript */ = {
 			isa = PBXShellScriptBuildPhase;
@@ -330,10 +318,15 @@
 			buildActionMask = 2147483647;
 			files = (
 			);
-			inputFileListPaths = (
+			inputPaths = (
+				"${PODS_ROOT}/Target Support Files/Pods-Runner/Pods-Runner-frameworks.sh",
+				"${BUILT_PRODUCTS_DIR}/shared_preferences_macos/shared_preferences_macos.framework",
+				"${BUILT_PRODUCTS_DIR}/url_launcher_macos/url_launcher_macos.framework",
 			);
 			name = "[CP] Embed Pods Frameworks";
-			outputFileListPaths = (
+			outputPaths = (
+				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/shared_preferences_macos.framework",
+				"${TARGET_BUILD_DIR}/${FRAMEWORKS_FOLDER_PATH}/url_launcher_macos.framework",
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
diff --git a/google_sign_in_dart/example/pubspec.lock b/google_sign_in_dart/example/pubspec.lock
index 6d2f1c3c..37b2f8e8 100644
--- a/google_sign_in_dart/example/pubspec.lock
+++ b/google_sign_in_dart/example/pubspec.lock
@@ -7,84 +7,84 @@ packages:
       name: _discoveryapis_commons
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.0"
+    version: "1.0.0"
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.5.0-nullsafety"
+    version: "2.5.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety"
+    version: "2.1.0"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety.2"
+    version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety"
+    version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.1.0"
   collection:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.15.0-nullsafety.2"
-  convert:
-    dependency: transitive
-    description:
-      name: convert
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.1"
+    version: "1.15.0"
   crypto:
     dependency: transitive
     description:
       name: crypto
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.5"
+    version: "3.0.1"
   extension_google_sign_in_as_googleapis_auth:
     dependency: "direct main"
     description:
       name: extension_google_sign_in_as_googleapis_auth
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.0"
+    version: "2.0.2"
   fake_async:
     dependency: transitive
     description:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.2.0"
+  ffi:
+    dependency: transitive
+    description:
+      name: ffi
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.0"
   file:
     dependency: transitive
     description:
       name: file
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.2.1"
+    version: "6.1.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -106,182 +106,189 @@ packages:
       name: google_sign_in
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.5.3"
+    version: "5.0.1"
   google_sign_in_dartio:
     dependency: "direct main"
     description:
       path: ".."
       relative: true
     source: path
-    version: "0.0.8"
+    version: "0.0.9"
   google_sign_in_platform_interface:
     dependency: transitive
     description:
       name: google_sign_in_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.2"
+    version: "2.0.1"
   google_sign_in_web:
     dependency: transitive
     description:
       name: google_sign_in_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.9.1+1"
+    version: "0.10.0"
   googleapis:
     dependency: "direct main"
     description:
       name: googleapis
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.55.0"
+    version: "2.0.0"
   googleapis_auth:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: googleapis_auth
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.12"
+    version: "1.1.0"
   html_unescape:
     dependency: transitive
     description:
       name: html_unescape
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.1+3"
+    version: "2.0.0"
   http:
     dependency: "direct main"
     description:
       name: http
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.2"
+    version: "0.13.1"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.3"
-  intl:
-    dependency: transitive
-    description:
-      name: intl
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.16.1"
+    version: "4.0.0"
   js:
     dependency: transitive
     description:
       name: js
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.1+1"
+    version: "0.6.3"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.10-nullsafety"
+    version: "0.12.10"
   meta:
     dependency: transitive
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.2"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety"
+    version: "1.8.0"
   path_provider_linux:
     dependency: transitive
     description:
       name: path_provider_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+2"
+    version: "2.0.0"
   path_provider_platform_interface:
     dependency: transitive
     description:
       name: path_provider_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.3"
+    version: "2.0.1"
+  path_provider_windows:
+    dependency: transitive
+    description:
+      name: path_provider_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   pedantic:
     dependency: "direct dev"
     description:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.2"
+    version: "1.11.0"
   platform:
     dependency: transitive
     description:
       name: platform
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.1"
+    version: "3.0.0"
   plugin_platform_interface:
     dependency: transitive
     description:
       name: plugin_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.2"
+    version: "2.0.0"
   process:
     dependency: transitive
     description:
       name: process
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.0.13"
+    version: "4.2.1"
   quiver:
     dependency: transitive
     description:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.5"
+    version: "3.0.1"
   shared_preferences:
     dependency: transitive
     description:
       name: shared_preferences
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.5.10"
+    version: "2.0.5"
   shared_preferences_linux:
     dependency: transitive
     description:
       name: shared_preferences_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.2+2"
+    version: "2.0.0"
   shared_preferences_macos:
     dependency: transitive
     description:
       name: shared_preferences_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+10"
+    version: "2.0.0"
   shared_preferences_platform_interface:
     dependency: transitive
     description:
       name: shared_preferences_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.3"
+    version: "2.0.0"
   shared_preferences_web:
     dependency: transitive
     description:
       name: shared_preferences_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.2+4"
+    version: "2.0.0"
+  shared_preferences_windows:
+    dependency: transitive
+    description:
+      name: shared_preferences_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -293,98 +300,112 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety"
+    version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.10.0-nullsafety"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.19-nullsafety"
+    version: "0.2.19"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.2"
+    version: "1.3.0"
   url_launcher:
     dependency: "direct main"
     description:
       name: url_launcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.5.0"
+    version: "6.0.3"
   url_launcher_linux:
     dependency: transitive
     description:
       name: url_launcher_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+1"
+    version: "2.0.0"
   url_launcher_macos:
     dependency: transitive
     description:
       name: url_launcher_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+7"
+    version: "2.0.0"
   url_launcher_platform_interface:
     dependency: transitive
     description:
       name: url_launcher_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.6"
+    version: "2.0.2"
   url_launcher_web:
     dependency: transitive
     description:
       name: url_launcher_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.1+1"
+    version: "2.0.0"
+  url_launcher_windows:
+    dependency: transitive
+    description:
+      name: url_launcher_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety.2"
+    version: "2.1.0"
+  win32:
+    dependency: transitive
+    description:
+      name: win32
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.5"
   xdg_directories:
     dependency: transitive
     description:
       name: xdg_directories
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.2"
+    version: "0.2.0"
 sdks:
-  dart: ">=2.10.0-0.0.dev <2.10.0"
-  flutter: ">=1.12.13+hotfix.5 <2.0.0"
+  dart: ">=2.12.0 <3.0.0"
+  flutter: ">=1.22.0"
diff --git a/google_sign_in_dart/example/pubspec.yaml b/google_sign_in_dart/example/pubspec.yaml
index ce6fc490..74379d52 100644
--- a/google_sign_in_dart/example/pubspec.yaml
+++ b/google_sign_in_dart/example/pubspec.yaml
@@ -1,22 +1,27 @@
 name: google_sign_in_dart_example
 description: Example app for google_sign_in_dart
 
+environment:
+  sdk: '>=2.12.0 <3.0.0'
+
 dependencies:
   flutter:
     sdk: flutter
-  http: ^0.12.2
-  url_launcher: ^5.5.0
-  googleapis: ^0.55.0
-  extension_google_sign_in_as_googleapis_auth: ^1.0.0
+  http: ^0.13.1
+  url_launcher: ^6.0.3
+  googleapis: ^2.0.0
+  googleapis_auth: ^1.1.0
+  extension_google_sign_in_as_googleapis_auth: ^2.0.2
 
-  google_sign_in: ^4.5.3
+  google_sign_in: ^5.0.1
   google_sign_in_dartio:
     path: ../
+  collection: ^1.15.0-nullsafety.4
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  pedantic: ^1.9.2
+  pedantic: ^1.11.0
 
 flutter:
   uses-material-design: true
\ No newline at end of file
diff --git a/google_sign_in_dart/lib/google_sign_in_dartio.dart b/google_sign_in_dart/lib/google_sign_in_dartio.dart
index 955d669f..064aad8d 100644
--- a/google_sign_in_dart/lib/google_sign_in_dartio.dart
+++ b/google_sign_in_dart/lib/google_sign_in_dartio.dart
@@ -13,11 +13,10 @@ import 'package:google_sign_in/google_sign_in.dart';
 import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart'
     as platform;
 import 'package:http/http.dart';
-import 'package:meta/meta.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:url_launcher/url_launcher.dart';
 
-part 'src/code_exchange_sing_in.dart';
+part 'src/code_exchange_sign_in.dart';
 part 'src/common.dart';
 part 'src/crypto.dart';
 part 'src/data_storage.dart';
@@ -30,14 +29,11 @@ typedef UrlPresenter = void Function(Uri uri);
 /// Implementation of the google_sign_in plugin in pure dart.
 class GoogleSignInDart extends platform.GoogleSignInPlatform {
   GoogleSignInDart._({
-    @required DataStorage storage,
-    @required String clientId,
-    @required UrlPresenter presenter,
-    String exchangeEndpoint,
-  })  : assert(storage != null),
-        assert(clientId != null),
-        assert(presenter != null),
-        _storage = storage,
+    required DataStorage storage,
+    required String clientId,
+    required UrlPresenter presenter,
+    String? exchangeEndpoint,
+  })  : _storage = storage,
         _clientId = clientId,
         _presenter = presenter,
         _exchangeEndpoint = exchangeEndpoint;
@@ -48,10 +44,10 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   /// the tokens is a secure, long-lived location that is accessible between
   /// different invocations of your application.
   static Future<void> register({
-    @required String clientId,
-    String exchangeEndpoint,
-    DataStorage storage,
-    UrlPresenter presenter,
+    required String clientId,
+    String? exchangeEndpoint,
+    DataStorage? storage,
+    UrlPresenter? presenter,
   }) async {
     presenter ??= (Uri uri) => launch(uri.toString());
 
@@ -79,17 +75,17 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
     );
   }
 
-  final String _exchangeEndpoint;
+  final String? _exchangeEndpoint;
   final String _clientId;
   final DataStorage _storage;
 
   UrlPresenter _presenter;
-  List<String> _scopes;
-  String _hostedDomain;
+  List<String>? _scopes;
+  String? _hostedDomain;
 
-  platform.GoogleSignInTokenData _tokenData;
-  String _refreshToken;
-  DateTime _expiresAt;
+  platform.GoogleSignInTokenData? _tokenData;
+  String? _refreshToken;
+  DateTime? _expiresAt;
 
   /// Used by the sign in flow to allow opening of a browser in a platform
   /// specific way.
@@ -99,16 +95,15 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   UrlPresenter get presenter => _presenter;
 
   set presenter(UrlPresenter value) {
-    assert(value != null);
     _presenter = value;
   }
 
   @override
   Future<void> init({
-    @required String hostedDomain,
+    String? hostedDomain,
     List<String> scopes = const <String>[],
     platform.SignInOption signInOption = platform.SignInOption.standard,
-    String clientId,
+    String? clientId,
   }) async {
     assert(clientId == null || clientId == _clientId,
         'ClientID ($clientId) does not match the one used to register the plugin $_clientId.');
@@ -118,7 +113,7 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
         'Check https://developers.google.com/identity/protocols/googlescopes '
         'for a list of valid OAuth 2.0 scopes.');
 
-    if (scopes == null || scopes.isEmpty) {
+    if (scopes.isEmpty) {
       _scopes = const <String>['openid', 'email', 'profile'];
     } else {
       _scopes = scopes;
@@ -128,7 +123,7 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   }
 
   @override
-  Future<platform.GoogleSignInUserData> signInSilently() async {
+  Future<platform.GoogleSignInUserData?> signInSilently() async {
     if (_haveValidToken) {
       return _storage.userData;
     } else if (_refreshToken != null) {
@@ -145,9 +140,9 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   }
 
   @override
-  Future<platform.GoogleSignInUserData> signIn() async {
+  Future<platform.GoogleSignInUserData?> signIn() async {
     if (_haveValidToken) {
-      final platform.GoogleSignInUserData userData = _storage.userData;
+      final platform.GoogleSignInUserData? userData = _storage.userData;
       if (userData == null) {
         await _fetchUserProfile();
       }
@@ -160,21 +155,21 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
 
   @override
   Future<platform.GoogleSignInTokenData> getTokens(
-      {String email, bool shouldRecoverAuth}) async {
+      {required String email, bool? shouldRecoverAuth}) async {
     if (_haveValidToken) {
-      return _tokenData;
+      return _tokenData!;
     } else if (_refreshToken != null) {
       // if refreshing the token fails, and shouldRecoverAuth is true, then we
       // will prompt the user to login again
       try {
         await _doTokenRefresh();
-        return _tokenData;
+        return _tokenData!;
       } catch (_) {}
     }
 
-    if (shouldRecoverAuth) {
+    if (shouldRecoverAuth!) {
       await _performSignIn(_scopes);
-      return _tokenData;
+      return _tokenData!;
     } else {
       throw PlatformException(
           code: GoogleSignInAccount.kUserRecoverableAuthError);
@@ -209,7 +204,7 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   }
 
   @override
-  Future<void> clearAuthCache({String token}) async {
+  Future<void> clearAuthCache({String? token}) async {
     await _revokeToken();
     _storage.clear();
     _initFromStore();
@@ -234,7 +229,8 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   Future<void> _revokeToken() async {
     if (_haveValidToken) {
       await get(
-        'https://oauth2.googleapis.com/revoke?token=${_tokenData.accessToken}',
+        Uri.parse(
+            'https://oauth2.googleapis.com/revoke?token=${_tokenData!.accessToken}'),
         headers: <String, String>{
           'content-type': 'application/x-www-form-urlencoded'
         },
@@ -244,16 +240,16 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
 
   Future<void> _fetchUserProfile() async {
     if (_haveValidToken) {
-      final String token = _tokenData.accessToken;
+      final String? token = _tokenData!.accessToken;
       final Response response = await get(
-        'https://openidconnect.googleapis.com/v1/userinfo',
+        Uri.parse('https://openidconnect.googleapis.com/v1/userinfo'),
         headers: <String, String>{
           'Authorization': 'Bearer $token',
         },
       );
 
       if (response.statusCode > 300) {
-        if (response.statusCode == 401){
+        if (response.statusCode == 401) {
           await signOut();
         }
         throw PlatformException(
@@ -268,23 +264,23 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
   }
 
   bool get _haveValidToken {
-    return _expiresAt != null && DateTime.now().isBefore(_expiresAt);
+    return _expiresAt != null && DateTime.now().isBefore(_expiresAt!);
   }
 
-  Future<void> _performSignIn(List<String> scopes) async {
+  Future<void> _performSignIn(List<String>? scopes) async {
     Future<Map<String, dynamic>> future;
     if (_exchangeEndpoint != null) {
       future = _codeExchangeSignIn(
-        scope: scopes.join(' '),
+        scope: scopes!.join(' '),
         clientId: _clientId,
         hostedDomains: _hostedDomain,
         presenter: presenter,
-        exchangeEndpoint: _exchangeEndpoint,
+        exchangeEndpoint: _exchangeEndpoint!,
         uid: _storage.id,
       );
     } else {
       future = _tokenSignIn(
-        scope: scopes.join(' '),
+        scope: scopes!.join(' '),
         clientId: _clientId,
         hostedDomains: _hostedDomain,
         presenter: presenter,
@@ -306,13 +302,13 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
     await _fetchUserProfile();
   }
 
-  Future<void> _doTokenRefresh() async {
+  Future<Map<String, dynamic>> _doTokenRefresh() async {
     assert(_exchangeEndpoint != null);
     assert(_refreshToken != null);
 
     final Response response = await post(
-      _exchangeEndpoint,
-      body: json.encode(<String, String>{
+      Uri.parse(_exchangeEndpoint!),
+      body: json.encode(<String, String?>{
         'refreshToken': _refreshToken,
         'clientId': _clientId,
       }),
@@ -327,6 +323,8 @@ class GoogleSignInDart extends platform.GoogleSignInPlatform {
     } else {
       return Future<Map<String, dynamic>>.error(response.body);
     }
+
+    throw Exception('Error refreshing token');
   }
 
   void _initFromStore() {
diff --git a/google_sign_in_dart/lib/src/code_exchange_sing_in.dart b/google_sign_in_dart/lib/src/code_exchange_sign_in.dart
similarity index 82%
rename from google_sign_in_dart/lib/src/code_exchange_sing_in.dart
rename to google_sign_in_dart/lib/src/code_exchange_sign_in.dart
index ab4e7895..ffdd74cd 100644
--- a/google_sign_in_dart/lib/src/code_exchange_sing_in.dart
+++ b/google_sign_in_dart/lib/src/code_exchange_sign_in.dart
@@ -10,18 +10,13 @@ part of '../google_sign_in_dartio.dart';
 /// Once the auth code comes back it make a post to [exchangeEndpoint] for
 /// to obtain the access and refresh tokens.
 Future<Map<String, dynamic>> _codeExchangeSignIn({
-  @required String clientId,
-  @required String exchangeEndpoint,
-  @required String scope,
-  @required UrlPresenter presenter,
-  String hostedDomains,
-  String uid,
+  required String clientId,
+  required String exchangeEndpoint,
+  required String scope,
+  required UrlPresenter presenter,
+  String? hostedDomains,
+  String? uid,
 }) async {
-  assert(clientId != null);
-  assert(exchangeEndpoint != null);
-  assert(presenter != null);
-  assert(scope != null);
-
   final Completer<Map<String, dynamic>> completer =
       Completer<Map<String, dynamic>>();
 
@@ -84,18 +79,18 @@ Future<Map<String, dynamic>> _codeExchangeSignIn({
 }
 
 Future<Map<String, dynamic>> _validateAndExchangeCodeResponse({
-  @required HttpRequest request,
-  @required String state,
-  @required String exchangeEndpoint,
-  @required String redirectUrl,
-  @required String clientId,
-  @required String codeVerifier,
+  required HttpRequest request,
+  required String state,
+  required String exchangeEndpoint,
+  required String redirectUrl,
+  required String clientId,
+  required String codeVerifier,
 }) {
   final Map<String, String> authResponse = request.requestedUri.queryParameters;
-  final String returnedState = authResponse['state'];
-  final String code = authResponse['code'];
+  final String? returnedState = authResponse['state'];
+  final String? code = authResponse['code'];
 
-  String message;
+  String? message;
   if (state != returnedState) {
     message = 'Invalid response from server (state did not match).';
   }
@@ -124,15 +119,15 @@ Future<Map<String, dynamic>> _validateAndExchangeCodeResponse({
 }
 
 Future<Map<String, dynamic>> _exchangeCode({
-  @required String exchangeEndpoint,
-  @required String redirectUrl,
-  @required String clientId,
-  @required String code,
-  @required String codeVerifier,
+  required String exchangeEndpoint,
+  required String redirectUrl,
+  required String clientId,
+  required String? code,
+  required String codeVerifier,
 }) async {
   final Response response = await post(
-    exchangeEndpoint,
-    body: json.encode(<String, String>{
+    Uri.parse(exchangeEndpoint),
+    body: json.encode(<String, String?>{
       'code': code,
       'codeVerifier': codeVerifier,
       'clientId': clientId,
diff --git a/google_sign_in_dart/lib/src/crypto.dart b/google_sign_in_dart/lib/src/crypto.dart
index a1c2396c..a7b6c1ad 100644
--- a/google_sign_in_dart/lib/src/crypto.dart
+++ b/google_sign_in_dart/lib/src/crypto.dart
@@ -13,10 +13,8 @@ const String _charset =
 /// See "Proof Key for Code Exchange by OAuth Public Clients (RFC 7636)
 /// <https://tools.ietf.org/html/rfc7636>"
 String _generateSecureRandomString(
-    [Random entropySource, int entropyBytes = 64]) {
+    [Random? entropySource, int entropyBytes = 64]) {
   entropySource ??= Random.secure();
-  assert(entropySource != null, 'entropySource cannot be null');
-  assert(entropyBytes != null, 'entropyBytes cannot be null');
 
   final StringBuffer buffer = StringBuffer();
   int remainingLength = entropyBytes;
diff --git a/google_sign_in_dart/lib/src/data_storage.dart b/google_sign_in_dart/lib/src/data_storage.dart
index b9204275..186c5c03 100644
--- a/google_sign_in_dart/lib/src/data_storage.dart
+++ b/google_sign_in_dart/lib/src/data_storage.dart
@@ -7,10 +7,8 @@ part of '../google_sign_in_dartio.dart';
 /// Helper class for persisting tokens between sessions
 class DataStorage {
   /// Create an instance that will persist the values using [store].
-  const DataStorage._({@required Store store, @required String clientId})
-      : assert(store != null),
-        assert(clientId != null),
-        _store = store,
+  const DataStorage._({required Store store, required String clientId})
+      : _store = store,
         _clientId = clientId;
 
   final Store _store;
@@ -31,27 +29,27 @@ class DataStorage {
   /// In case there is no user logged in this value is the id of the last user
   /// that was logged in. This id can be used as a hint when the user tries to
   /// login again.
-  String get id => _store.get(_getKey(_kIdKey));
+  String? get id => _store.get(_getKey(_kIdKey));
 
   /// Saves the JSON Web Token (JWT) that contains digitally signed identity
   /// information about the user.
-  String get idToken => _store.get(_getKey(_kIdTokenKey));
+  String? get idToken => _store.get(_getKey(_kIdTokenKey));
 
-  set idToken(String value) => _setValue(_kIdTokenKey, value);
+  set idToken(String? value) => _setValue(_kIdTokenKey, value);
 
   /// Saves the token that your application sends to authorize a Google API
   /// request.
-  String get accessToken => _store.get(_getKey(_kAccessTokenKey));
+  String? get accessToken => _store.get(_getKey(_kAccessTokenKey));
 
-  set accessToken(String value) => _setValue(_kAccessTokenKey, value);
+  set accessToken(String? value) => _setValue(_kAccessTokenKey, value);
 
   /// Saves the remaining lifetime of the access token.
-  DateTime get expiresAt {
-    final String date = _store.get(_getKey(_kExpirationAtKey));
+  DateTime? get expiresAt {
+    final String? date = _store.get(_getKey(_kExpirationAtKey));
     return date != null ? DateTime.parse(date) : null;
   }
 
-  set expiresAt(DateTime value) {
+  set expiresAt(DateTime? value) {
     _setValue(_kExpirationAtKey, value?.toIso8601String());
   }
 
@@ -60,18 +58,20 @@ class DataStorage {
   /// Refresh tokens are present if you provided a
   /// [GoogleSignInDart._exchangeEndpoint] value and are valid until the
   /// user revokes access.
-  String get refreshToken => _store.get(_getKey(_kRefreshTokenKey));
+  String? get refreshToken => _store.get(_getKey(_kRefreshTokenKey));
 
-  set refreshToken(String value) => _setValue(_kRefreshTokenKey, value);
+  set refreshToken(String? value) => _setValue(_kRefreshTokenKey, value);
 
   /// Retrieve the authentication data after sign in.
   platform.GoogleSignInTokenData get tokenData {
     if (idToken != null || accessToken != null) {
       return platform.GoogleSignInTokenData(
-          idToken: idToken, accessToken: accessToken);
+        idToken: idToken,
+        accessToken: accessToken,
+      );
     }
 
-    return null;
+    return platform.GoogleSignInTokenData();
   }
 
   set tokenData(platform.GoogleSignInTokenData data) {
@@ -83,7 +83,7 @@ class DataStorage {
   ///
   /// Returns an empty list if no authorization has take place yet.
   List<String> get scopes {
-    final String value = _store.get(_getKey(_kScopeKey));
+    final String? value = _store.get(_getKey(_kScopeKey));
     if (value == null || value.isEmpty) {
       return <String>[];
     }
@@ -136,12 +136,12 @@ class DataStorage {
   }
 
   /// Retrieve information about this signed in user based on the id_token.
-  platform.GoogleSignInUserData get userData {
+  platform.GoogleSignInUserData? get userData {
     if (idToken != null) {
       return platform.GoogleSignInUserData(
-        id: _store.get(_getKey(_kIdKey)),
+        id: _store.get(_getKey(_kIdKey))!,
         displayName: _store.get(_getKey(_kNameKey)),
-        email: _store.get(_getKey(_kEmailKey)),
+        email: _store.get(_getKey(_kEmailKey))!,
         photoUrl: _store.get(_getKey(_kPictureKey)),
         idToken: idToken,
       );
@@ -150,7 +150,7 @@ class DataStorage {
     return null;
   }
 
-  void _setValue(String key, String value) {
+  void _setValue(String key, String? value) {
     if (value == null) {
       _store.remove(_getKey(key));
     } else {
@@ -170,7 +170,7 @@ abstract class Store {
   void remove(String key);
 
   /// Get the value at specified [key] or nul if it doesn't exists.
-  String get(String key);
+  String? get(String key);
 
   /// Remove all the values store.
   void clearAll();
@@ -182,8 +182,8 @@ class _SharedPreferencesStore extends Store {
   final SharedPreferences _preferences;
 
   @override
-  String get(String key) {
-    return _preferences.get(key);
+  String? get(String key) {
+    return _preferences.get(key) as String?;
   }
 
   @override
diff --git a/google_sign_in_dart/lib/src/token_sign_in.dart b/google_sign_in_dart/lib/src/token_sign_in.dart
index cc27d491..eb52a182 100644
--- a/google_sign_in_dart/lib/src/token_sign_in.dart
+++ b/google_sign_in_dart/lib/src/token_sign_in.dart
@@ -10,16 +10,12 @@ part of '../google_sign_in_dartio.dart';
 /// Using this implementation will not provide a refresh token, that means that
 /// the user will need to login again after the access token expires (~1 hour)
 Future<Map<String, dynamic>> _tokenSignIn({
-  @required String clientId,
-  @required String scope,
-  @required UrlPresenter presenter,
-  String hostedDomains,
-  String uid,
+  required String clientId,
+  required String scope,
+  required UrlPresenter presenter,
+  String? hostedDomains,
+  String? uid,
 }) async {
-  assert(presenter != null);
-  assert(clientId != null);
-  assert(scope != null);
-
   final Completer<Map<String, dynamic>> completer =
       Completer<Map<String, dynamic>>();
 
@@ -76,11 +72,11 @@ Future<Map<String, dynamic>> _tokenSignIn({
 Future<Map<String, String>> _validateTokenResponse(
     HttpRequest request, String state) async {
   final Map<String, String> authResponse = request.requestedUri.queryParameters;
-  final String returnedState = authResponse['state'];
-  final String accessToken = authResponse['access_token'];
-  final String idToken = authResponse['id_token'];
+  final String? returnedState = authResponse['state'];
+  final String? accessToken = authResponse['access_token'];
+  final String? idToken = authResponse['id_token'];
 
-  String message;
+  String? message;
   if (state != returnedState) {
     message = 'Invalid response from server (state did not match).';
   }
diff --git a/google_sign_in_dart/pubspec.lock b/google_sign_in_dart/pubspec.lock
index 2c1c10a0..7052b61a 100644
--- a/google_sign_in_dart/pubspec.lock
+++ b/google_sign_in_dart/pubspec.lock
@@ -7,70 +7,70 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.5.0-nullsafety"
+    version: "2.5.0"
   boolean_selector:
     dependency: transitive
     description:
       name: boolean_selector
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety"
+    version: "2.1.0"
   characters:
     dependency: transitive
     description:
       name: characters
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety.2"
+    version: "1.1.0"
   charcode:
     dependency: transitive
     description:
       name: charcode
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety"
+    version: "1.2.0"
   clock:
     dependency: transitive
     description:
       name: clock
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.1.0"
   collection:
     dependency: transitive
     description:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.15.0-nullsafety.2"
-  convert:
-    dependency: transitive
-    description:
-      name: convert
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "2.1.1"
+    version: "1.15.0"
   crypto:
     dependency: "direct main"
     description:
       name: crypto
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.5"
+    version: "3.0.1"
   fake_async:
     dependency: transitive
     description:
       name: fake_async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.2.0"
+  ffi:
+    dependency: transitive
+    description:
+      name: ffi
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.0"
   file:
     dependency: transitive
     description:
       name: file
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.2.1"
+    version: "6.1.0"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -92,161 +92,168 @@ packages:
       name: google_sign_in
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.5.3"
+    version: "5.0.1"
   google_sign_in_platform_interface:
     dependency: "direct main"
     description:
       name: google_sign_in_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.2"
+    version: "2.0.1"
   google_sign_in_web:
     dependency: transitive
     description:
       name: google_sign_in_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.9.1+1"
+    version: "0.10.0"
   html_unescape:
     dependency: "direct main"
     description:
       name: html_unescape
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.1+3"
+    version: "2.0.0"
   http:
     dependency: "direct main"
     description:
       name: http
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.2"
+    version: "0.13.1"
   http_parser:
     dependency: transitive
     description:
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.3"
-  intl:
-    dependency: transitive
-    description:
-      name: intl
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "0.16.1"
+    version: "4.0.0"
   js:
     dependency: transitive
     description:
       name: js
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.1+1"
+    version: "0.6.3"
   matcher:
     dependency: transitive
     description:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.10-nullsafety"
+    version: "0.12.10"
   meta:
     dependency: "direct main"
     description:
       name: meta
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.2"
+    version: "1.3.0"
   path:
     dependency: transitive
     description:
       name: path
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety"
+    version: "1.8.0"
   path_provider_linux:
     dependency: transitive
     description:
       name: path_provider_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+2"
+    version: "2.0.0"
   path_provider_platform_interface:
     dependency: transitive
     description:
       name: path_provider_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.3"
+    version: "2.0.1"
+  path_provider_windows:
+    dependency: transitive
+    description:
+      name: path_provider_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   pedantic:
     dependency: transitive
     description:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.0"
+    version: "1.11.0"
   platform:
     dependency: transitive
     description:
       name: platform
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.2.1"
+    version: "3.0.0"
   plugin_platform_interface:
     dependency: transitive
     description:
       name: plugin_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.2"
+    version: "2.0.0"
   process:
     dependency: transitive
     description:
       name: process
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.0.13"
+    version: "4.2.1"
   quiver:
     dependency: transitive
     description:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.5"
+    version: "3.0.1"
   shared_preferences:
     dependency: "direct main"
     description:
       name: shared_preferences
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.5.10"
+    version: "2.0.5"
   shared_preferences_linux:
     dependency: "direct main"
     description:
       name: shared_preferences_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.2+2"
+    version: "2.0.0"
   shared_preferences_macos:
     dependency: "direct main"
     description:
       name: shared_preferences_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+10"
+    version: "2.0.0"
   shared_preferences_platform_interface:
     dependency: transitive
     description:
       name: shared_preferences_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.3"
+    version: "2.0.0"
   shared_preferences_web:
     dependency: transitive
     description:
       name: shared_preferences_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.2+4"
+    version: "2.0.0"
+  shared_preferences_windows:
+    dependency: transitive
+    description:
+      name: shared_preferences_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -258,98 +265,112 @@ packages:
       name: source_span
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.8.0-nullsafety"
+    version: "1.8.0"
   stack_trace:
     dependency: transitive
     description:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.10.0-nullsafety"
+    version: "1.10.0"
   stream_channel:
     dependency: transitive
     description:
       name: stream_channel
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety"
+    version: "2.1.0"
   string_scanner:
     dependency: transitive
     description:
       name: string_scanner
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.0-nullsafety"
+    version: "1.1.0"
   term_glyph:
     dependency: transitive
     description:
       name: term_glyph
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.2.0-nullsafety"
+    version: "1.2.0"
   test_api:
     dependency: transitive
     description:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.19-nullsafety"
+    version: "0.2.19"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.3.0-nullsafety.2"
+    version: "1.3.0"
   url_launcher:
     dependency: "direct main"
     description:
       name: url_launcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "5.5.0"
+    version: "6.0.3"
   url_launcher_linux:
     dependency: transitive
     description:
       name: url_launcher_linux
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+1"
+    version: "2.0.0"
   url_launcher_macos:
     dependency: "direct main"
     description:
       name: url_launcher_macos
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.0.1+7"
+    version: "2.0.0"
   url_launcher_platform_interface:
     dependency: transitive
     description:
       name: url_launcher_platform_interface
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.0.6"
+    version: "2.0.2"
   url_launcher_web:
     dependency: transitive
     description:
       name: url_launcher_web
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.1+1"
+    version: "2.0.0"
+  url_launcher_windows:
+    dependency: transitive
+    description:
+      name: url_launcher_windows
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.0"
   vector_math:
     dependency: transitive
     description:
       name: vector_math
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0-nullsafety.2"
+    version: "2.1.0"
+  win32:
+    dependency: transitive
+    description:
+      name: win32
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.5"
   xdg_directories:
     dependency: transitive
     description:
       name: xdg_directories
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.1.2"
+    version: "0.2.0"
 sdks:
-  dart: ">=2.10.0-0.0.dev <2.10.0"
-  flutter: ">=1.12.13+hotfix.5 <2.0.0"
+  dart: ">=2.12.0 <3.0.0"
+  flutter: ">=1.22.0"
diff --git a/google_sign_in_dart/pubspec.yaml b/google_sign_in_dart/pubspec.yaml
index 2084ac8b..15a9eae0 100644
--- a/google_sign_in_dart/pubspec.yaml
+++ b/google_sign_in_dart/pubspec.yaml
@@ -1,26 +1,26 @@
 name: google_sign_in_dartio
 description: Flutter package for Google Sign-In built in dart and support both Mobile and Desktop environments.
-version: 0.0.8
+version: 0.0.9
 homepage: https://github.com/fluttercommunity/firebase_dart_sdk/tree/develop/google_sign_in_dart
 commit: 89794a635a5efad6705e3d7ccc29e8139318d947
 
 environment:
-  sdk: ">=2.8.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   flutter:
     sdk: flutter
-  google_sign_in: ^4.5.3
-  google_sign_in_platform_interface: ^1.1.2
-  shared_preferences: ^0.5.10
-  shared_preferences_macos: ^0.0.1+10
-  shared_preferences_linux: ^0.0.2+2
-  url_launcher: ^5.5.0
-  url_launcher_macos: ^0.0.1+7
-  meta: ^1.2.2
-  crypto: ^2.1.5
-  http: ^0.12.2
-  html_unescape: ^1.0.1+3
+  google_sign_in: ^5.0.1
+  google_sign_in_platform_interface: ^2.0.1
+  shared_preferences: ^2.0.5
+  shared_preferences_macos: ^2.0.0
+  shared_preferences_linux: ^2.0.0
+  url_launcher: ^6.0.3
+  url_launcher_macos: ^2.0.0
+  meta: ^1.3.0
+  crypto: ^3.0.1
+  http: ^0.13.1
+  html_unescape: ^2.0.0
 
 dev_dependencies:
   flutter_test: