FirebaseAuth.Instance is null xamarin forms

Question

FirebaseAuth.Instance is null in xamarin forms tried updating package removing package, unable to solve the problem

public async Task<bool> LoginUser(string Email, string Password)
    {            
        try
        {
            await FirebaseAuth.Instance.SignInWithEmailAndPasswordAsync(Email, Password);
            return true;
        }
        catch (FirebaseAuthWeakPasswordException ex)
        {
            throw new Exception(ex.Message);
        }
        catch (FirebaseAuthInvalidCredentialsException ex)
        {
            throw new Exception(ex.Message);
        }   
        catch (FirebaseAuthInvalidUserException ex)
        {
            throw new Exception("There is no user record corresponding to this identifier");
        }            
        catch (Exception ex)
        {
            throw new Exception("There was an unkown Error."); 
        }   
    }

Answer 1

1. install Xamarin.GooglePlayServices.Base
2. include google-services.json with the 'GoogleServicesJson' build action
3. invoke Firebase.FirebaseApp.InitializeApp(this); in MainActivity.onCreate() method.