try {
  final _googleSignIn = GoogleSignIn(
    scopes: [
      'email',
      'https://www.googleapis.com/auth/contacts.readonly',
    ],
  );
  final googleSignInAccount = await _googleSignIn.signIn();
  final googleSignInAuthentication = await googleSignInAccount.authentication;
  final code = googleSignInAuthentication.serverAuthCode;
  print(code);
} catch (error) {
  print(error);
}