Add an example and fix example in readme

Author: kevmoo

.travis.yml

@@ -1,7 +1,7 @@
 language: dart
 
 dart:
-- 2.0.0
+- 2.1.0
 - dev
 
 dart_task:

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.1.2
 
 * Fix a number of lints affecting package maintenance score.
+* Update minimum Dart SDK to `2.1.0`.
 
 ## 0.1.1+3
 

README.md

@@ -11,16 +11,19 @@ underlying [`http.Client`][Client]:
 import 'package:http/http.dart' as http;
 import 'package:http_retry/http_retry.dart';
 
-main() async {
-  var client = new RetryClient(new http.Client());
-  print(await client.read("http://example.org"));
-  await client.close();
+Future<void> main() async {
+  final client = RetryClient(http.Client());
+  try {
+    print(await client.read('http://example.org'));
+  } finally {
+    client.close();
+  }
 }
 ```
 
 By default, this retries any request whose response has status code 503
 Temporary Failure up to three retries. It waits 500ms before the first retry,
 and increases the delay by 1.5x each time. All of this can be customized using
-the [`new RetryClient()`][new RetryClient] constructor.
+the [`RetryClient()`][new RetryClient] constructor.
 
 [new RetryClient]: https://pub.dev/documentation/http_retry/latest/http_retry/RetryClient/RetryClient.html

example/example.dart

@@ -0,0 +1,15 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:http/http.dart' as http;
+import 'package:http_retry/http_retry.dart';
+
+Future<void> main() async {
+  final client = RetryClient(http.Client());
+  try {
+    print(await client.read('http://example.org'));
+  } finally {
+    client.close();
+  }
+}

pubspec.yaml

@@ -5,7 +5,7 @@ description: HTTP client middleware that automatically retries requests.
 homepage: https://github.com/dart-lang/http_retry
 
 environment:
-  sdk: '>=2.0.0 <3.0.0'
+  sdk: '>=2.1.0 <3.0.0'
 
 dependencies:
   async: ^2.0.7