异步转同步方案（含超时机制）

 const int TimeoutMs = 30;
        private static readonly ManualResetEventSlim _manualResetEvent = new ManualResetEventSlim(false);
        private static readonly object LockObj = new object();

        static string GetInfoStr()
        {
            var rez = "超时";
            Monitor.TryEnter(LockObj, TimeoutMs * 1000);
            try
            {
                //临界区代码
                var random = new Random();
                _ = Task.Run(() =>
                {
                    var newran = random.Next(100, 250);
                    // Debug.WriteLine($"正常等待时间{newran}");
                    Thread.Sleep(newran);
                    rez = $"正常执行{j}";
                    j++;
                    _manualResetEvent.Set();
                });
                _manualResetEvent.Wait(TimeSpan.FromSeconds(TimeoutMs));
                Debug.WriteLine("SpinCount:" + _manualResetEvent.SpinCount);
                _manualResetEvent.Reset();
            }
            finally
            {
                Monitor.Exit(LockObj);
            }

            return rez;
        }