Google Sign In

You need to have your app already published on Google Play. so when you publish the app on google play, come back to this step

First go to your firebase console and go to the Authentication -> sign in method -> add new provider

then go to your google play console, copy the SHA code and paste it in firebase.

1. Open google play console

2. select your app

3. search for App integrity

4. 
5. click on it, then click on app signing

6. 
7. copy the SHA-1 code and SHA-256 and paste them in firebase...

Setup In Firebase

open your firebase project and then go to project settings

then scroll down and add fingerprint