Using await on HttpClient in wpf project

I just following a sample in calling HttpClient in sync mode, it works fine in a Console application.

However, when I move it to a wpf application, the program hanged without any return.

I try to isolate the problem by building a separate class to handle a dummy request to visit www.google.com.

It seems that the application hang in calling client.GetAsync, may I know if there has any thing need to be changed from console application to wpf in this case?

Please find the source of both the console application and wpf as below,

Console application - works fine:

using System;
using System.Threading.Tasks;
using System.Net.Http;

namespace ca03
{
    static class action
    {
        static async Task<string> DownloadPageAsync()
        {
            // ... Target page.
            string page = "http://www.google.com/";

            // ... Use HttpClient.
            using (HttpClient client = new HttpClient())
            using (HttpResponseMessage response = await client.GetAsync(page))
            using (HttpContent content = response.Content)
            {
                // ... Read the string.
                string result = await content.ReadAsStringAsync();

                // ... Display the result.
                if (result != null &&
                result.Length >= 50)
                {
                    Console.WriteLine(result.Substring(0, 50) + "...");
                }
                return result;
            }
        }

        public static string goDownload()
        {
            Task<string> x = DownloadPageAsync();
            string result = x.Result;
            return result;
        }

    }

    class Program
    {
        static void Main(string[] args)
        {
            string data = action.goDownload();
            Console.WriteLine(data);

            Console.ReadLine();
        }
    }
}

WPF application: (just a plain project with a button added) - hang in GetAsync

using System;
using System.Threading.Tasks;
using System.Windows;
using System.Net.Http;

namespace wpf02
{

    static class action
    {
        static async Task<string> DownloadPageAsync()
        {
            // ... Target page.
            string page = "http://www.google.com/";

            // ... Use HttpClient.
            using (HttpClient client = new HttpClient())
            using (HttpResponseMessage response = await client.GetAsync(page))
            using (HttpContent content = response.Content)
            {
                // ... Read the string.
                string result = await content.ReadAsStringAsync();
                return result;
            }
        }

        public static string goDownload()
        {
            Task<string> x = DownloadPageAsync();
            string result = x.Result;
            return result;
        }

    }


    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void button_Click(object sender, RoutedEventArgs e)
        {
            string data = action.goDownload();
            Console.WriteLine(data);
        }
    }
}