message: doc: update document demo
diff: @@ -105,9 +105,9 @@ GET /error
  {
  "method": "error",
  "date": 1346846400,
  - "errType": "myError",
  - "message": "",
  - "stack": "",
  + "errType": "TypeError",
  + "message": "Cannot read property 'name' of null",
  + "stack": "2017-11-29 15:01:20 Error: read ECONNRESET",
  "traceId": "1231455",
  "path": "/xxx/xx.log"
  }
  