title: How to add map to message in protobuf3
body: <p>I'm trying to create message with map that is supported since protobuf3. I cannot figure out how to add a map to message.</p>
  
  <p>Proto file fragment:</p>
  
  <pre><code>message MyData {
      map&lt;string, Queue&gt; myMap = 1;
  
      message Queue {
          repeated float position = 1;
    }
  }
  </code></pre>
  
  <p>Java fragment:</p>
  
  <pre><code>MyData.Builder dataBuilder = SnowflakeData.newBuilder();
  dataBuilder. ???
  </code></pre>
  
  <p>I can get <code>dataBuilder.getMyMap()</code>, but i have problem with "set"</p>
  
  <p>Thanks</p>