Use base64 0.21. (#724)

* Use base64 0.21.

* Use a non-deprecated base64 encoding function.

Author: khuey

lambda-runtime/Cargo.toml

@@ -43,5 +43,5 @@ tokio-stream = "0.1.2"
 lambda_runtime_api_client = { version = "0.8", path = "../lambda-runtime-api-client" }
 serde_path_to_error = "0.1.11"
 http-serde = "1.1.3"
-base64 = "0.20.0"
+base64 = "0.21.0"
 http-body = "0.4"

lambda-runtime/src/types.rs

@@ -1,4 +1,5 @@
 use crate::{Config, Error};
+use base64::prelude::*;
 use bytes::Bytes;
 use http::{HeaderMap, HeaderValue, StatusCode};
 use serde::{Deserialize, Serialize};
@@ -208,7 +209,7 @@ impl ToStreamErrorTrailer for Error {
     fn to_tailer(&self) -> String {
         format!(
             "Lambda-Runtime-Function-Error-Type: Runtime.StreamError\r\nLambda-Runtime-Function-Error-Body: {}\r\n",
-            base64::encode(self.to_string())
+            BASE64_STANDARD.encode(self.to_string())
         )
     }
 }