Flutter Google play services

I am creating a flutter game which utilise the Google play games. I use the game_services package.

When I tried to signIn, the logs says like this:

code:

void signin() async {
    try {
      print('account before: $account');
      account = await GamesServices.signIn();
      print('account: $account');
    } catch (e) {
      print('Error on signing: $e');
    }
}

@override
  void initState() {
    signin();
    super.initState();
  }

Logs: I/PlayService( 2169): isAuthenticated: true toString: com.google.android.gms.games.AuthenticationResult@c64b8d0 I/signin ( 2169): success I/flutter ( 2169): account: null

You can see even after saying success, the account String is empty.

I had completed these steps

1. added game_services package
2. included app_id in AndroidManifest
3. created OAuth 2.0 Client ID and auth consent screen inside Google cloud project
4. added xml file inside android/app/src/main/res/values/games-ids.xml

I want to know why account is null.

I solved it by changing the code like this:

try {
      await GamesServices.signIn();
      if (await GamesServices.isSignedIn) {
        // user is signed
      }
}

Also make sure you added the SHA1 fingerprint of both debug and production inside the Credentials (OAuth Clients).