fix all warnings

Author: mythz

.github/workflows/publish.yml

@@ -102,7 +102,7 @@ jobs:
         run: dart format --output=none --set-exit-if-changed .
 
       - name: Analyze project
-        run: dart analyze --fatal-infos
+        run: dart analyze
 
       - name: Run tests
         run: dart test

example/main.dart

@@ -1,7 +1,7 @@
 import 'package:servicestack/client.dart';
 import 'test.dtos.dart';
 
-main() async {
+Future<void> main() async {
   var client = JsonServiceClient("https://test.servicestack.net");
 
   var request = Hello(name: "World");