Update Future.cs

seems it was needed...

Author: calumma-robert

GoogleSignIn/Future.cs

@@ -71,6 +71,7 @@ internal Future(FutureAPIImpl<T> impl) {
     /// <param name="tcs">Tcs.</param>
     internal IEnumerator WaitForResult(TaskCompletionSource<T> tcs) {
       yield return new WaitUntil(() => !Pending);
+      yield return null;
       if (Status == GoogleSignInStatusCode.CANCELED) {
         tcs.SetCanceled();
       } else if (Status == GoogleSignInStatusCode.SUCCESS ||
@@ -84,6 +85,7 @@ internal IEnumerator WaitForResult(TaskCompletionSource<T> tcs) {
     internal async Task WaitForResultAsync(TaskCompletionSource<T> tcs)
     {
       while (Pending) await Task.Yield();
+      await Task.Yield();
       if (Status == GoogleSignInStatusCode.CANCELED) {
         tcs.SetCanceled();
       } else if (Status == GoogleSignInStatusCode.SUCCESS ||
@@ -94,4 +96,4 @@ internal async Task WaitForResultAsync(TaskCompletionSource<T> tcs)
       }
     }
   }
-}
+}