Follow these instructions

Get the right sha1 key match details

Variant: debugAndroidTest Config: debug Store: /Users/..../..../.../android/app/debug.keystore Alias: androiddebugkey MD5: 65:01:AE:C5:89:21:98:57:CB:D9:17:76:55:52:34:4F SHA1: FA:D4:3F:12:DF:F4:DA:B0:04:41:1A:49:E8:DB:A3:91:AE:FC:D0:9C SHA-256: 8A:36:45:A1:CA:21:4C:7F:35:1F:32:66:1B:64:FA:06:7C:FB:3C:0B:FB:57:3D:19:17:BC:6E:55:5F:C4:FD:ED

1. Create android client id with package and sha1 key In advance setting bottom of verify owner enable checkbox Custom URI scheme
2. Generate a web client id without any redirect url
3. Also add permissions in scope Oauth consent screen tab ./auth/userinfo.email ./auth/userinfo.profile openid

And aslo in scope also add Test users your mail which will be verified in google sign in button

Now copy the web client id and use in code