Dart 2 support?

[theKAKAN]

I'm getting errors with Flutter beta 2, which uses Dart 2.
I tried running it with flutter run --no-preview-dart-2 and it worked.
Here's the error, with beta 2 and Dart 2.
type 'Future<dynamic>' is not a subtype of type 'Future<int>'
Location:

  Future<int> play(String url, {bool isLocal: false, double volume: 1.0}) =>
      _channel.invokeMethod('play', {"playerId": playerId, "url": url, "isLocal": isLocal, 'volume': volume});

in audioplayer.dart
Running flame_example
Well, here's a screenshot from VS Code:

The line in which the error is found is Flame.audio.loop('music.ogg');

[theKAKAN]

Tried 0.5.1, no errors but sound was not being played.
In 0.5.2, everything works fine. Thank you :)