gistfile1.cs

    class Program
    {
        static void Main(string[] args)
        {
            ServicePointManager.DefaultConnectionLimit = 2;

            var tasks = new Task[10];
            for (int i = 0; i < 10; i++)
            {
                tasks[i] = Run();
            }
            Task.WhenAll(tasks).Wait();

            using (HttpClient client = new HttpClient())
            {
                for (int i = 0; i < 10; i++)
                {
                    tasks[i] = Run(client);
                }
                Task.WhenAll(tasks).Wait();
            }
            

        }

        private static async Task Run()
        {

            HttpClient client = new HttpClient();
            var response = await client.GetAsync("http://www.tugberkugurlu.com");
        }

        static async Task Run(HttpClient client)
        {
            var response = await client.GetAsync("http://www.tugberkugurlu.com");
        }
    }