How to return datas as array for child components with relationship as JSON in lumen 5.5

I have a basic relationship for posts, which has relationship with its user and its category. When i return it with json i only get array for the Parent component (i.e) only for the posts. My user datas are only coming as a instance. ResultingI cannot grab it in javascript. Here is my function and response,

 public function index()
   {
       $posts =  Post::with('user', 'category')->get();

       return response()->json($posts);
    }

My response is

  [
  {
    "id": 1,
    "user_id": 7,
    "title": "tis is  title",
    "description": "Occaecati ad ipsum esse alias officiis exercitationem. Nihil dolor autem sed id fugiat eveniet numquam. In ipsum aliquam quod.",
    "category_id": "4",
    "slug": "this-is-title",
    "created_at": "2017-09-24 11:40:55",
    "updated_at": "2017-09-25 00:18:29",

    "user": {
        "id": 7,
        "username": "lucious.greenholt",
        "name": "7",
        "email": "gregorio37@bailey.com",
    },

    "category": {
        "id": 4,
        "name": "ashly.farrell",
        "created_at": "2017-09-24 11:40:56",
        "updated_at": "2017-09-24 11:40:56"
     }
   }
 ]

See the user and category not coming as an array. Can someone help?