static void Main(string[] args)
        {
            int i = 1;
            while (true)
            {
                doWork2(i);
                Thread.Sleep(1000);
                i++;

            }
        }
        /// <summary>
        /// async/await 语法用看起来像写同步代码的方式来优雅地处理异步操作
        /// </summary>
        /// <param name="mission"></param>
        static async void doWork(int mission)
        {
            await Task.Run(()=> {
                Console.WriteLine("异步开始=====>"+mission);
                Thread.Sleep(3000);
                Console.WriteLine("异步结束=====>"+mission);
            });
            Console.WriteLine("观察者====>" + mission);
        }


        static  void doWork2(int mission)
        {
             Task.Run(() => {
                Console.WriteLine("异步开始=====>" + mission);
                Thread.Sleep(3000);
                Console.WriteLine("异步结束=====>" + mission);
            });
            Console.WriteLine("观察者====>" + mission);
        }