title: Better way of prefix matching in a short string in Go: strings or regexp
body: <p>I know that the string I'll get will be short ( &lt; 50 chars). 
  I also know that my substring will be matched exactly once (or won't be matched at all), and that it will appear de facto at the beginning of the string. </p>
  
  <p>I cannot decide whether to use <code>strings.Contains</code>, e.g., <code>strings.Contains("123-ab-foo", "123-ab")</code>, or <code>regexp</code>.  I want the fastest way obviously. </p>
  
  <p>Example of the use case:  </p>
  
  <pre><code>if strings.Contains(current_string, MY_CONST){
       // do smth 
   }
  </code></pre>