title: Regex for starting with alphanumeric and hyphen, underscore later in string
body: <p>I'm trying to write a regexp in golang that matches strings that start as alphanumeric and can have an underscore or hyphen after, but not starting with a hyphen or underscore.</p>
  
  <p>Here is what I could come up with, but this matches alphanumeric and hyphen underscore anywhere</p>
  
  <pre><code>[A-Za-z0-9_-]
  </code></pre>
  
  <p>So something like sea-food would match or seafood or sea_food, but not -seafood nor _seafood.</p>