title: Get XML namespace prefix in Go using Unmarshal
body: <p>I would like to know if it is possible to get the XML namespace prefix using the 
  <code>Unmarshal</code> method in <code>encoding/xml</code>.</p>
  
  <p>For example, I have: </p>
  
  <pre><code>&lt;application xmlns="http://wadl.dev.java.net/2009/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
  &lt;/application&gt;
  </code></pre>
  
  <p>I would like to know how to retrieve the <code>xs</code> defining the prefix for XMLSchema, without having to use the <code>Token</code> method.</p>