title: Make a cobra Command flag required
body: <p>I've created a cobra command and added a flag:</p>
  
  <pre><code>cmd.Flags().StringVarP(&amp;primaryIP, "primary-ip", "p", "", "Help text")
  </code></pre>
  
  <p>Is there a way to make it required other than checking the value myself and returning an error?</p>