title: Flutter : 'onError' is deprecated on runZoned function
body: <p>I got this error message when I using newest Flutter v 1.17.1 and Dart 2.8.2 version on main.dart file,</p>
  
  <blockquote>
    <p>'onError' is deprecated and shouldn't be used. Use runZonedGuarded instead.
    Try replacing the use of the deprecated member with the replacement.</p>
  </blockquote>
  
  <p>and this is the code,</p>
  
  <pre><code>  runZoned&lt;Future&lt;Null&gt;&gt;(() async {
      runApp(MyApp());
    }, onError: (error, stackTrace) async {
      await FlutterCrashlytics().reportCrash(error, stackTrace, forceCrash: false);
    });
  }
  </code></pre>
  
  <p>Any solution to get rid of this error message?</p>