MissingPluginException(Не е намерена реализация за метод init на канал plugins.flutter.io/google_sign_in) FLUTTER

Пуснах flutter doctor и не съобщава за грешка. Удостоверяването на google работи добре в IOS, но не и за android. Хората са склонни да казват, че актуализацията върши работата, но тя не работи за мен. Тя се срива на: _currentUser = await _googleSignIn.signIn();

    try {
        _currentUser = await _googleSignIn.signIn();
        final GoogleSignInAuthentication googleSignInAuthentication =
            await _currentUser.authentication;

        final AuthCredential credential = GoogleAuthProvider.getCredential(
          accessToken: googleSignInAuthentication.accessToken,
          idToken: googleSignInAuthentication.idToken,
        );
        final authResult = await _auth.signInWithCredential(credential);
        final user = await _auth.currentUser();
    }catch(ex){}

Файлът pubspec е както следва:

      name: app
      description: A new Flutter project.

      publish_to: 'none' # Remove this line if you wish to publish to                     
      pub.dev

      version: 1.0.0+1

      environment:
        sdk: ">=2.7.0 <3.0.0"

      dependencies:
        flutter:
          sdk: flutter

        cupertino_icons: ^0.1.3
        modal_progress_hud: ^0.1.3
        http: ^0.12.2
        shared_preferences: ^0.5.8


        firebase_core: ^0.4.5
        firebase_auth: ^0.16.1
        cloud_firestore: ^0.13.7
        flutter_facebook_login: ^3.0.0
        flutter_facebook_auth: ^0.2.3
        google_sign_in: ^4.5.1
        flutter_signin_button: ^1.0.0





      dev_dependencies:
        flutter_test:
          sdk: flutter


      flutter:

        uses-material-design: true

        assets:
           - assets/images/
        fonts:
        - family: Questrial
          fonts:
          - asset: assets/fonts/Questrial-Regular.ttf
            weight: 900