title: Golang map put if absent?
body: <p>I have a map of the format:</p>
  <p><code>map[string]map[string]int</code></p>
  <p>In this main map, I want to do something like <code>putIfAbsent(&quot;key&quot;, new HashMap&lt;&gt;()</code> as we have in Java. What is a clean and shorthand way to do it in Go?</p>