C#方法执行超时退出

 　　　　[HttpGet]
        public async Task<string> TestUU()
        {
            ParentTsk().Wait();
            Console.WriteLine("Hello World!");
            return "ok";
        }

　　　　　public async static Task ParentTsk()
        {
            CancellationTokenSource cts = new CancellationTokenSource();
            cts.CancelAfter(20);
            Task<string> workTsk = Task.Run(async () => await WorkTsk());
            Task<string> watchTsk = Task.Run(async () => await WatchTsk(cts.Token));
            Task<string>[] tskArray = new Task<string>[] { watchTsk, workTsk };

            var rsltTsk = await Task.WhenAny(tskArray);
            Console.WriteLine($"执行结果{rsltTsk.Result}");

        }

 　　　　public async static Task<string> WorkTsk()
        {

            string fileName = @"d:\tstFile.txt";
            List<int> lstINt = Enumerable.Range(0, 5000).ToList();
            foreach (var item in lstINt)
            {
                await System.IO.File.AppendAllTextAsync(fileName, $"{item}|");
            }

            return "it is WorkTsk";
        }

        public async static Task<string> WatchTsk(CancellationToken token)
        {
            while (!token.IsCancellationRequested)
            {
                await Task.Delay(10);
            }
            return "it is WatchTsk";
        }