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

[✓] Flutter (Channel stable, v1.17.1, on Mac OS X 10.15.4 19E287, locale en-GB)
    • Flutter version 1.17.1 at /users/faiyyazkhatri/StudioProjects/flutter
    • Framework revision f7a6a7906b (8 days ago), 2020-05-12 18:39:00 -0700
    • Engine revision 6bc433c6b6
    • Dart version 2.8.2

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /users/faiyyazkhatri/Library/Android/sdk
    • Platform android-29, build-tools 29.0.3
    • ANDROID_HOME = /users/faiyyazkhatri/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.4.1, Build version 11E503a
    • CocoaPods version 1.9.1

[✓] Android Studio (version 3.6)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 45.1.1
    • Dart plugin version 192.8052
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] Connected device (1 available)
    • iPhone 11 Pro Max • 690EC0B1-6D79-42BE-8447-4746C5E2FAAD • ios • com.apple.CoreSimulator.SimRuntime.iOS-13-4 (simulator)

• No issues found!