CancellationToken 取消机制

        [HttpGet("GetFile")]
        public async Task<string> GetFile(string file)
        {
            CancellationTokenSource cts = new CancellationTokenSource();//通过CancellationTokenSource产生Token
            cts.CancelAfter(3000);//超时时间3s
            cts.Token.Register(() => Console.WriteLine($"超时取消"));//注册一个取消请求后的执行事件
            return await DownFile(file, cts.Token);
        }
        private async Task<string> DownFile(string file, CancellationToken cancellationToken)
        {
            for (int i = 1; i <= 10; i++)
            {
                Console.WriteLine($"执行进度{i}");
                if (cancellationToken.IsCancellationRequested)
                {
                    return "超时";
                }
                await Task.Delay(1000);
            }
            return file + ":下载完成";
        }

        [HttpGet("GetFile2")]
        public async Task<string> GetFile(string file, CancellationToken cancellationToke)
        {
            cancellationToke.Register(() => Console.WriteLine($"超时取消"));//注册一个取消请求后的执行事件
            return await DownFile(file, cancellationToke);
        }