title: Get sum() in two columns in Laravel 5.4
body: <p>I have this table (<code>Pickups</code>):</p>
  
  <pre><code>+-----------+------------+-------------+------------+
  | worker_id | box_weight | bag_weight |    date    |
  +-----------+------------+-------------+------------+
  |         1 |          2 |           5 | 11-07-2018 |
  |         1 |          7 |           9 | 11-07-2018 |
  |         2 |          8 |          11 | 11-07-2018 |
  |         2 |          7 |          12 | 11-07-2018 |
  +-----------+------------+-------------+------------+
  </code></pre>
  
  <p>and I want in Laravel 5.4 Eloquent database engine get the sum of the box_weight and the bag_weight like this:</p>
  
  <pre><code>+-----------+-----------------+-----------------+------------+
  | worker_id | sum(box_weight) | sum(bag_weight) |    date    |
  +-----------+-----------------+-----------------+------------+
  |         1 |               9 |              14 | 11-07-2018 |
  |         2 |              15 |              23 | 11-07-2018 |
  +-----------+-----------------+-----------------+------------+
  </code></pre>
  
  <p>Until now I could only retrieve the sum of a single column not the both in the same call.</p>