Sequence Thread Starting and wait

thread_semaphore.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    internal class Program
    {

        private static Semaphore _pool = new Semaphore(initialCount: 1, maximumCount: 1);

        static void Main(string[] args)
        {
            DoA();
            DoB();
        }

        private static void DoA()
        {
            new Thread(() =>
            {
                Thread.Sleep(1000);
                try
                {
                    _pool.WaitOne();
                    Console.WriteLine("A Begin");
                    Thread.Sleep(1000);
                    Console.WriteLine("A Process");
                    Thread.Sleep(1000);
                }
                finally
                {
                    _pool.Release();
                    Console.WriteLine("A End");
                }
            }).Start();
        }

        private static void DoB()
        {
            new Thread(() =>
            {
                Thread.Sleep(1000);
                try
                {
                    _pool.WaitOne();
                    Console.WriteLine("B Begin");
                    Thread.Sleep(1000);
                    Console.WriteLine("B Process");
                    Thread.Sleep(1000);
                }
                finally
                {
                    _pool.Release();
                    Console.WriteLine("B End");
                }
            }).Start();
        }

    }
}