HttpClient异步调用时数据返回问题

[sunpiny]

用HttpClient读网页，已定义全局 client。以下代码运行正常，加断点可发现sResult有读到的内容

Private Async Function GetInfo(url As String) As Task
        client.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64)")
        Dim sResult As String = Await client.GetStringAsync(url)
        'Do something
        Return 
    End Function

为了能为调用程序返回数据，改为

Private Async Function GetInfo(url As String) As Task(Of String)
        client.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64)")
        Dim sResult As String = Await client.GetStringAsync(url)
        Return sResult
End Function

结果程序就挂起了，永远执行不到 Return sResult，什么原因呢？