public async Task LockExecuteTestAsync()
        {
            const string key = "lockTest";

            var func = new Func <int, int, Task <int> >(async(a, b) =>
            {
                // _testOutputHelper.WriteLine(
                //     $"thread-{Thread.CurrentThread.ManagedThreadId.ToString()} get the lock.");
                await Task.Delay(1000);
                return(await Task.FromResult(a + b));
            });

            var rdm = new Random();

            for (var i = 0; i < 3; i++)
            {
                new Thread(async() =>
                {
                    var success = _redis.LockExecute(key, Guid.NewGuid().ToString(), func,
                                                     out var result,
                                                     TimeSpan.MaxValue,
                                                     3000, rdm.Next(0, 10), 0);

                    if (success)
                    {
                        var res = await(result as Task <int>);
                        _testOutputHelper.WriteLine(
                            $"result is {res}.\t{DateTime.Now.ToLongTimeString()}");
                    }
                    else
                    {
                        _testOutputHelper.WriteLine(
                            $"failed to get lock.\t{DateTime.Now.ToLongTimeString()}");
                    }
                })
                {
                    IsBackground = true
                }