How to upload userId along an image to server swift

I would like to upload a picture along another integer to my server. Currently, I only send the image to server using Alamofire from the ios app. See code below:

func uploadPicture() {
let url = "my-server-url"
let image = #imageLiteral(resourceName: "capitan")
let imageData = UIImageJPEGRepresentation(image, 1.0)!
Alamofire.upload(
  multipartFormData: { multipartFormData in
    multipartFormData.append(imageData, withName: "photo", fileName: "photo.jpg", mimeType: "image/jpg")
  },
  to: url,
  encodingCompletion: { encodingResult in
    switch encodingResult {
    case .success(let upload, _, _):
      upload.responseJSON { response in
        debugPrint(response)
      }
    case .failure(let encodingError):
      print(encodingError)
    }
  }
)}

While in the backend, I am using nodejs along mutler.

var upload = multer({ storage : storage}).any(); 
 app.post('/upload', function(req, resp) {
   upload(req, resp, function(err) {
   console.log("req:" + req);
   if(!err) {
     console.log("Upload complete.");
     resp.send(JSON.stringify(true));
   } else {
     console.log(err);
     resp.send(JSON.stringify(false));
   }
  });
});

via user2232305