snapshot.connectionState == waiting about firebase_auth_demo_flutter HOT 1 CLOSED

When I try to debug and see whats happening, for this:

 _jupiterAuthSubscription = _jupiterAuthService.onAuthStateChanged.listen((User user) {

it goes to a method which returns:
Unhandled exception:\nBad state: Stream has already been listened to.\n#0 _StreamController._subscribe (dart:async/stream_controller.dart:668:7)\n#1 _ControllerStream._createSubscription (dart:async/stream_controller.dart:818:19)\n#2 _StreamImpl.listen (dart:async/stream_impl.dart:472:9)\n#3 Stream.isEmpty (dart:async/stream.dart:1015:25)\n#4 _ControllerStream.Eval ()\n#5 JupiterAuthService.onAuthStateChanged (package:jupiter/services/jupiter_auth_service.dart:18:42)\n#6 AuthServiceAdapter._setup (package:jupiter/services/auth_service_adapter.dart:25:52)\n#7 new AuthServiceAdapter (package:jupiter/services/auth_service_adapter.dart:11:5)\n#8 MyApp.build. (package:jupiter/main.dart:19:27)\n#9 BuilderStateDelegate.initDelegate (package:provider/src/delegate_widget.dart:244:14)\n#10 _DelegateWidgetState._initDelegate (package:provider/src/delegate_widget.dart:117:21)\n#11 _DelegateWidgetState.initState (package:provider/src/delegate_widget.dart:109:...

but, inside of the JupiterAuthService, i have the same as MockAuthService:

class JupiterAuthService implements AuthService {
  User _currentUser;

  final StreamController<User> _onAuthStateChangedController =
      StreamController<User>();

  @override
  Stream<User> get onAuthStateChanged => _onAuthStateChangedController.stream;

(in the last line, i got that exception)

from firebase_auth_demo_flutter.