File upload in express returns status 200 but file is not uploaded

Just like as the title says, I am trying to upload a file to a remote server using Angular's ngFileUpload and as middleware, I use express' connect-multiparty.

The Angular part looks like this:

            var upload = Upload.upload({
                url: 'api/uploadAttachments',
                method: 'POST',
                data: {
                    file: file
                },
                params: {
                    id: $scope.project.id
                }
            });


            upload.then(function (res) {
                console.log(res);
            });

and then on node:

api.post('/uploadAttachments', multipartyMiddleware, UserController.uploadFile);

then on UserController.js

 var requestLib = require("request");

 UserController = function() {};

 UserController.prototype.uploadFile = function(req, res) {
     requestLib({
        url: 'https://www.myserverexample.com/api/uploads',
        method: "POST",
        headers: {
            'Accept' : 'application/json, text/plain, */*',
            'Content-Type': 'multipart/form-data'
        },
        qs: {
            pid: req.query.id
        },
        data: {
            deliveryAttachment: req.files.file
        }
     }, function (error, response, body) {      
         res.send(body);
     });
 }

 module.exports = new UserController();

After I upload, I get this object in return on the frontend:

{data: "", status: 200, config: Object, statusText: "OK", headers: function}

Am I missing something here? Any help is definitely appreciated! :)

via Growlithe