public void TestCancellationToken()
        {
            CancellationTokenSource ct   = new CancellationTokenSource();
            Task <JObject>          task = _client.ListIndexesAsync(ct.Token);

            ct.Cancel();
            try
            {
                task.GetAwaiter().GetResult();
                Assert.Fail("Should thow an error");
            }
            catch (TaskCanceledException)
            {
                // Pass
            }
        }