private async void btnTestConn_Click(object sender, EventArgs e)
{
  async Task<bool> test_networkAsync()
  {
    Stopwatch sw = new Stopwatch();
    try
    {
      //sw.Start();
      using (var client = new System.Net.WebClient())
      using (var stream = await client.OpenReadTaskAsync("https://www.youtube.com"))
      {
        //sw.Stop();
        //Console.WriteLine(sw.Elapsed);
        return true;
      }
    }
    catch
    {
      return false;
    }
  }

  // I put it in the loop in order to testing.
  for (int i = 0; i < 5; ++i)
  {
    await test_networkAsync();
  }
}