asStream method Null safety
override
Creates a Stream containing the result of this future.
The stream will produce single data or error event containing the completion result of this future, and then it will close with a done event.
If the future never completes, the stream will not produce any events.
Implementation
@override
Stream<T> asStream() {
final StreamController<T> controller = StreamController<T>();
controller.add(_value);
controller.close();
return controller.stream;
}