private async void OnGoogleAuthCompleted(object sender, AuthenticatorCompletedEventArgs e)
        {
            this.DismissViewController(true, null);

            var googleService = new GoogleService();
            var email         = await googleService.GetEmailAsync(e.Account.Properties["token_type"], e.Account.Properties["access_token"]);

            GoogleButton.SetTitle(email, UIControlState.Normal);
        }