Futures in Dart / flutter_sound examples not working - flutter

Question

Start tinkering with Dart/Flutter, I'm trying to record and play audio. Examples provided in this library: https://github.com/dooboolab/flutter_sound show async code in Dart using Futures.
Future<String> result = await flutterSound.startRecorder(null);
result.then(path) {
print('startRecorder: $path');
_recorderSubscription = flutterSound.onRecorderStateChanged.listen((e) {
DateTime date = new DateTime.fromMillisecondsSinceEpoch(e.currentPosition.toInt());
String txt = DateFormat('mm:ss:SS', 'en_US').format(date);
});
}
However this code doesn't even compile at my system so Im wondering what I'm missing. In order to compile this code I have to change it to something like:
Future<String> result = widget._flutterSound.startRecorder(null);
result.then((path) {
print('startRecorder: $path');
var _recorderSubscription = widget._flutterSound.onRecorderStateChanged.listen((e) {
DateTime date = new DateTime.fromMillisecondsSinceEpoch(e.currentPosition.toInt());
print(date);
});
});
What am I missing?

Answer 1

Have you try this:
Future<String> result() async => flutterSound.startRecorder(null);
when you working with futures: async and await: https://dart.dev/codelabs/async-await
The async and await keywords provide a declarative way to define asynchronous functions and use their results. Remember these two basic guidelines when using async and await:
To define an async function, add async before the function body.
The await keyword works only in async functions.