onShareAppMessage里面如何通过异步获取数据然后返回？

onShareAppMessage: function (res) {

   let shareId;
     wx.request({       

     url: 'https://xxx/xxx',       

     data: {para:para},       

     success: function (res) {
        shareId = res.data.shareId
      }
     })   

   return {path: shareId}

}