user_provider.dart

/// * si usamos Provider

void main() => runApp(
	StateNotifierProvider<UserStateNotifier, UserState>(
		create: (_) => UserStateNotifier(),
			child: MyApp(),
		),
);

...

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

		final userState = context.watch<UserStateNotifier>();

    return Scaffold(
      body: Center(
        child: Text('${userState.runtimeType}'),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          context.read<UserStateNotifier>().logIn(User());
        },
      ),
    );
  }
}