title: How to get key in loop slice in text/template?
body: <p>For example</p>
  
  <pre><code>{{ range $k, $v := .rec}}
  {{ $k }} :: {{ $v }}
  {{ end }}
  </code></pre>
  
  <p>Catch error <code>panic: template: let:2:19: executing "let" at &lt;.rec&gt;: can't evaluate field rec in type []string</code>. </p>