title: How to push multiple columns' value within group
body: <p>It seems my query will won't act as my expect</p>
  
  <p>I want to group by <code>name</code> and mapping location1 and location2 into an array called <code>locations</code></p>
  
  <h1>Data</h1>
  
  <pre><code>{name: "Jack", localtion1: "Taiwan", localtion2: "France"},
  {name: "Jack", localtion1: "Japan", localtion2: "Taiwan"},
  {name: "Mary", localtion1: "China", localtion2: "Taiwan"}
  </code></pre>
  
  <h1>Expected result</h1>
  
  <pre><code>{
      name: "Jack",
      localtions: ["Taiwan", "France", "Japan"]
  },
  {name: "Mary", localtions: ["China", "Taiwan"]}
  </code></pre>
  
  <h1>Query</h1>
  
  <pre><code>db.collection.aggregate([
      {
          $group: {
              _id: "$name",
              "localtions":{
                  $addToSet: "$localtion1"
              },
              "localtions":{
                  $addToSet: "$localtion2"
              }            
              count: { $sum: 1 }
          }
      },
      {
          $project: {
              name: "$_id",
              localtions: "$localtions",
              _id: 0
          }
      },    
  ])
  </code></pre>