我正在尝试将Twitter auth整合到我的Flutter应用程序中。我正在遵循FlutterFire文档，但我抛出了一个错误。我想知道是否在我的终端或Twitter登录插件上存在问题。下面是我的代码：

Future<UserCredential> signInWithTwitter() async {
    // Create a TwitterLogin instance
    final twitterLogin = new TwitterLogin(
        apiKey: '<1qOvE68aiVbk4URSARlfm0758>',
        apiSecretKey: ' <wQHWRYBweiV5DvEecSUTeSbnT6uwB6080D4vz6WDyY1geT8Paz>',
        redirectURI: '<twitter-firebase-auth>://');

    // Trigger the sign-in flow
    final authResult = twitterLogin.login();

    // Create a credential from the access token
    final twitterAuthCredential = TwitterAuthProvider.credential(
      accessToken: authResult.authToken!,
      secret: authResult.authTokenSecret!,
    );

    // Once signed in, return the UserCredential
    return await FirebaseAuth.instance
        .signInWithCredential(twitterAuthCredential);
  }

我得到以下错误：

The getter 'authToken' isn't defined for the type 'Future<AuthResult>'.
Try importing the library that defines 'authToken', correcting the name to the name of an existing getter, or defining a getter or field named 'authToken'.