In response to the use of Promise return ctx.body, received '404 Not Found'. 
In response to the use of Promise return ctx.body, received '404 Not Found'. But my mongodb is showing that the data was written. This troubled me, look forward to help.
```javascript
router.get('/api/login', function *(next) {
  let request = this.request;
  let response = this.response;
  let params = request.query;
  userInfo.set({
    document: {
      user: params.name,
      password: params.password
    }
  })
  .then(res => {
    response.body = {
      code: 0,
      data: {
        uid: res.uid,
      }
    };
  })
  .catch(err => {
    response.body = {
      code: 999999,
      error: err
    }
  })
  yield next;
})
```