title: Reflect.Value.FieldByName causing Panic
body: <p>I'm getting the following error when calling the .FieldByName method of a reflected value, the exact error is :-</p>
  
  <pre><code>panic: reflect: call of reflect.Value.FieldByName on ptr Value
  </code></pre>
  
  <p>and the code is :-</p>
  
  <pre><code>s := reflect.ValueOf(&amp;value).Elem() (value is a struct)
  metric := s.FieldByName(subval.Metric).Interface() (subval.Metric is a string)
  </code></pre>
  
  <p>I understand this isn't much, but this is all the information I can get.</p>
  
  <p>Here's a link to the code on Go Playground: <a href="http://play.golang.org/p/E038cPOoGp" rel="noreferrer">http://play.golang.org/p/E038cPOoGp</a></p>