Flutter sign in with Google in Android (without firebase)

There seems to be missing a guide for Google sign in with flutter, without firebase. Guides for firebase are in abundance, but if for any reason you want to go bare with google sign in, you are on your own.

So let’s discover what is necessary for Google sign in with flutter;
Most of it is also relevant for any other framework (Android native, react-native etc’).

Our steps are:
- Generate signed key for your android app
- Registering the app in Google cloud services
- Using…