title: Bind multiple values in gonic-gin
body: <p>I have a form like this:</p>
  
  <pre><code>&lt;form action="post" method="post"&gt;
              &lt;select name="message" multiple&gt;
                  &lt;option value="volvo"&gt;Volvo&lt;/option&gt;
                  &lt;option value="saab"&gt;Saab&lt;/option&gt;
                  &lt;option value="opel"&gt;Opel&lt;/option&gt;
                  &lt;option value="audi"&gt;Audi&lt;/option&gt;
              &lt;/select&gt;
              &lt;input type="submit"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>How do I get all messages by using <a href="https://github.com/gin-gonic/gin" rel="nofollow">gonic-gin</a> Bind method?</p>