C# async等待和不等待

代码：

class Program
    {
        private static void Main(string[] args)
        {
            Console.WriteLine("start0");
            var tt = CountCharactersAsync(null);
            Console.WriteLine("end0");

            Console.WriteLine("start1");
            var t = CountCharactersAsync(null);
            t.Wait();  //等待任务结束
            Console.WriteLine("end1");

            Console.Read();
        }


        private static async Task<int> CountCharactersAsync(string address)
        {
            Console.WriteLine("CountCharactersAsync-start");
            if (string.IsNullOrEmpty(address))
            {
                await Task.Run(() => Thread.Sleep(2000));

                Console.WriteLine("CountCharactersAsync-end");
                return 3000;
            }
            else
            {
                Console.WriteLine("CountCharactersAsync-end");
                return 10;
            }
        }
    }