title: mongo aggregation query with mgo driver
body: <p>I have the following query in mongodb:</p>
  <pre><code>db.devices.aggregate({
  $match: {userId: &quot;v73TuQqZykbxFXsWo&quot;, state: true}},
  {
    $project: {
      userId: 1,
      categorySlug: 1,
      weight: { 
        $cond: [ 
          {&quot;$or&quot;: [  
            {$eq: [&quot;$categorySlug&quot;, &quot;air_fryer&quot;] }, 
            {$eq: [&quot;$categorySlug&quot;, &quot;iron&quot;] } 
          ] }, 
        0, 1] } 
      } },  
      {$sort: {weight: 1}},
      { $limit : 10 }
  );
  </code></pre>
  <p>I'm trying to write this in Go using the mgo driver but not able to wrap my head around this at all!</p>
  <p>How do I translate this to a Go mgo query?</p>