Make flutter app force a user to choose an account with FirebaseAuth and GoogleSignInAuthentication

Use GoogleSignInAccount.disconnect() before signing out to revoke the previous authentication:

await _googleSignIn.disconnect();await FirebaseAuth.instance.signOut();

Harold's answer used to work for me, but recently the GoogleSignIn().currentUser appears null for some devices I tested, and then the disconnect function won't work. So, what solved that problem was ensuring it is signed in to Google.

final googleCurrentUser =        GoogleSignIn().currentUser ?? await GoogleSignIn().signIn();    if (googleCurrentUser != null)      await GoogleSignIn().disconnect().catchError((e, stack) {        FirebaseCrashlytics.instance.recordError(e, stack);      });    await _auth.signOut();

A simple way to go about it :-In your sign out method just use

_auth.signOut();

Now inside Google Sign In package, inside google_sign_in.dart

 Future<GoogleSignInAccount> signIn() {    final Future<GoogleSignInAccount> result =        _addMethodCall(GoogleSignInPlatform.instance.signIn, canSkipCall: false);    bool isCanceled(dynamic error) =>        error is PlatformException && error.code == kSignInCanceledError;    return result.catchError((dynamic _) => null, test: isCanceled);  }

Find the above method & set the canSkipCall parameter as false

final Future<GoogleSignInAccount> result =        _addMethodCall(GoogleSignInPlatform.instance.signIn, canSkipCall: false);

This will enable choosing a user every time you try to sign in