GetResponseAsync in Xamarin.Social never completes

I'm trying to make use of Twitter5Service in Xamarin.Social, but I can't get it to perform a request.

I created a Twitter account in Settings, and GetAccountsAsync returns this account.
However GetResponseAsync never finishes:

static readonly Twitter5Service Twitter5 = new Twitter5Service ();

void Test ()
{
    Twitter5.GetAccountsAsync ().ContinueWith (t => {
        var acc = t.Result.ToList () [0];
        var req = service.CreateRequest ("GET", new Uri ("https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name=twitterapi&count=2"), acc);

        req.GetResponseAsync ().ContinueWith (_ => {
            Console.WriteLine ("I'm never here!");
        });
    });
}

What I am doing wrong?