xxxxxxxxxx
go in=>
android>gradlew>open with>terminal
if(terminal reading plugin is not downloaded then it will
pop option to install it just above the editor)
now in termial it will read it and will show SHA1,SHA256 keys and other information
we have to add fingerprint in our firebase project in and add SHA1/SHA256
any of the key now the error will be gone and auth will be successful
xxxxxxxxxx
SOLUTION
1. GO TO GCP ->
2. ENABLED API & SERVICES
3. CREDENTIALS
4. GET THE OAuth 2.0 Client ID (WEB CLIENT)
ADD TO CONFIG SAMPLE
_googleSignIn = GoogleSignIn(
clientId: widget.appConfig.clientId, // Client ID
scopes: widget.appConfig.scopes, // https://www.googleapis.com/auth/contacts.readonly
);