public static async Task<string> GetAsync(string url, IEnumerable<KeyValuePair<string, string>> formDatas, IEnumerable<KeyValuePair<string, string>> headers, IEnumerable<KeyValuePair<string, string>> defaultHeaders = null)
        {
            formDatas.For(d => url += $"{(url.EndsWith('&') ? "" : "?")}{d.Key}={WebUtility.UrlEncode(d.Value ?? "")}&");
            url = url.TrimEnd('&');
            HttpClient client = new HttpClient();
            defaultHeaders.For(h => client.DefaultRequestHeaders.Add(h.Key, h.Value));
            var request = new HttpRequestMessage() { RequestUri = new Uri(url), Method = HttpMethod.Get };
            headers.For(h => request.Headers.Add(h.Key, h.Value));
            return (await (await client.SendAsync(request)).Content.ReadAsByteArrayAsync()).ToUTF8String();
        }

        public  IActionResult Async()
        {
            return Success(MyMethod());
        }


        static async Task<int> MyMethod()
        {
            for (int i = 0; i < 5; i++)
            {
                Console.WriteLine("Async start:" + i.ToString() + "..");
                await Task.Delay(1000); //模拟耗时操作
            }
            return 0;
        }

using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp5
{
    class Program
    {
        static void Main(string[] args)
        {

            ThreadStart t = new ThreadStart(new Action(() => {
                Parallel.For(1, 500, (i) => {
                    //code
                    GetAsync();
                });
            }));
            Thread tx = new Thread(t);
            tx.IsBackground = true;
            tx.Start();
            Console.ReadKey();
        }
        public static async void GetAsync()
        {
            HttpClient client = new HttpClient();
            var request = new HttpRequestMessage() { RequestUri = new Uri("http://localhost:50367/api/Test/Async"), Method = HttpMethod.Get };
            var a= (await (await client.SendAsync(request)).Content.ReadAsByteArrayAsync());
            Console.WriteLine(System.Text.Encoding.Default.GetString(a));
        }

    }
}

       public IActionResult Async()
        {
            return Success(MyMethod());
        }

        //public IActionResult Async()
        //{
        //    Random rd = new Random();
        //    return Success(rd.Next(1, 10));
        //}


        static async Task<int> MyMethod()
        {
            await Task.Delay(1000); //模拟耗时操作
            Random rd = new Random();
            return rd.Next(1, 10);
        }

        public async Task<IActionResult> Async()
        {
            await MyMethod();
            Random rd = new Random();
            return Success(rd.Next(1, 10));
        }


        static async Task<int> MyMethod()
        {
            await Task.Delay(1000); //模拟耗时操作
            Random rd = new Random();
            return rd.Next(1, 10);
        }