获取UserId GoogleActions

Question

我试图在Firebase中为我的谷歌用户获取userId，但显然它是未定义的

dialogflowFirebaseFulfillment
 ReferenceError: userId is not defined
    at IncomingMessage.resp.on (/user_code/index.js:73:17)
    at emitNone (events.js:91:20)
    at IncomingMessage.emit (events.js:185:7)
    at endReadableNT (_stream_readable.js:974:12)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickDomainCallback (internal/process/next_tick.js:128:9)

这是我的代码

    const REQUEST_PERMISSION_ACTION = 'request_permission';
    const userUID = app.getUser().userId;
    const userName = app.getUserName().displayName;
    console.log(userUID, 'USERRRRRRID');

我该怎么做才能得到userId？