using System;

using System.Threading;

using System.Threading.Tasks;

​

namespace aa

{

    class Program

    {

        static void Main(string[] args)

        {

            Program p = new Program();

            p.Run();

            Program b = new Program();

            b.Run();

        }

        public async void Run()

        {

            Console.WriteLine(ALProgram.AsyncLocalVar);

            await DoSOmeAsync();

            Console.WriteLine(ALProgram.AsyncLocalVar);

        }

​

        public static Task DoSOmeAsync()

        {

            ALProgram.AsyncLocalVar = 5;

            Console.WriteLine(ALProgram.AsyncLocalVar);

            var bb = Task.FromResult("aaaa");

​

            return bb;

        }

    }

    class ALProgram

    {

        private static AsyncLocal<int?> asyncLocalVar = new AsyncLocal<int?>();

        public static int AsyncLocalVar

        {

            get => asyncLocalVar.Value ?? 99;

            set => asyncLocalVar.Value = new int?(value);

        }

    }

}

​