gistfile1.cs

using (var client = new HttpClient())
{
    var authTokenBytes = Encoding.UTF8.GetBytes("auth_key:");
    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(authTokenBytes));

    await client.PostAsync("https://push.ducksboard.com/v/widget_id", new { value = timer.ElapsedMilliseconds }, new JsonMediaTypeFormatter());
}