I am playing with async await feature of C#. Things work as expected when I use it with UI thread. But when I use it in a non-UI thread it doesn't work as expected. Consider the code below

private void Click_Button(object sender, RoutedEventArgs e)
    {
        var bg = new BackgroundWorker();
        bg.DoWork += BgDoWork;
        bg.RunWorkerCompleted += BgOnRunWorkerCompleted;
        bg.RunWorkerAsync();
    }

    private void BgOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs runWorkerCompletedEventArgs)
    {
    }

    private async void BgDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
    {
        await Method();
    }


    private static async Task Method()
    {
        for (int i = int.MinValue; i < int.MaxValue; i++)
        {
            var http = new HttpClient();
            var tsk = await http.GetAsync("http://www.ebay.com");
        }
    }

When I execute this code, background thread don't wait for long running task in Method to complete. Instead it instantly executes the BgOnRunWorkerCompleted after calling Method. Why is that so? What am I missing here?

P.S: I am not interested in alternate ways or correct ways of doing this. I want to know what is actually happening behind the scene in this case? Why is it not waiting?