class Program
{
    public static void Main(string[] args)
    {
        Thread.CurrentThread.Name = "main";
        Console.WriteLine("Start Thread: " + Thread.CurrentThread.Name);
        Hello().GetAwaiter().GetResult();
        Console.WriteLine("End Thread: " + Thread.CurrentThread.Name);
        Thread.Sleep(100);
    }

    public static async Task Hello()
    {
        Console.WriteLine("Current Thread at Start Hello: " + Thread.CurrentThread.Name);
        await Task.Run(() =>
        {
            Thread.CurrentThread.Name = "task";
            Console.WriteLine("Current Thread at Task: " + Thread.CurrentThread.Name);
            Console.WriteLine("Hello World");
        });
        Thread.CurrentThread.Name = "async";
        Console.WriteLine("Current Thread at End Hello: " + Thread.CurrentThread.Name);
    }
}

Start Thread: main
Current Thread at Start Hello: main
Current Thread at Task: task
Hello World
Current Thread at End Hello: async
End Thread: main

private const int INITIAL_SIZE = 32;
internal volatile IThreadPoolWorkItem[] m_array = new IThreadPoolWorkItem[INITIAL_SIZE];
private volatile int m_mask = INITIAL_SIZE - 1;