Program.cs

private static async Task<string> DownloadStringWithTimeout(string location)
{
    using (var client = new HttpClient())
    {
        var downloadTask = client.GetStringAsync(location);
        var timeoutTask = Task.Delay(TimeSpan.FromSeconds(3));

        var completedTask = await Task.WhenAny(downloadTask, timeoutTask);

        if (completedTask == timeoutTask)
            return null;

        return await downloadTask;
    }
}