This is a very basic implementation of using Google as a sign-in authentication provider for your Flutter Apps.
Medium Article
Please follow the instructions in the following dependency packages: Google Sign In Package (https://pub.dev/packages/google_sign_in) Firebase Authentication (https://pub.dev/packages/firebase_auth)
These are some links on things to keep in mind while debugging the Firebase Authentication setup, creation of your Firebase account and setting up Firebase for both IOS and Android in your respective projects:
https://stackoverflow.com/questions/54557479/flutter-and-google-sign-in-plugin-platformexceptionsign-in-failed-com-google https://developers.google.com/android/guides/client-auth https://developer.android.com/studio/build/multidex
https://firebase.google.com/docs/android/setup
https://firebase.google.com/docs/ios/setup
https://www.youtube.com/watch?v=DqJ_KjFzL9I
Thanks!