title: How to go:generate stringer constants from multiple packages?
body: <p>I have a struct like this: </p>
  
  <pre><code>.foo/bar/constants.go
  .foo/constants.go
  .main.go 
  </code></pre>
  
  <p>In <code>main.go</code> I declare the type:</p>
  
  <pre><code>package agepack
  type EventType uint
  //go:generate stringer -type EventType
  const (
      FirstType EventType iota
      SecondType
      ....
  )
  </code></pre>
  
  <p>In each <code>constants.go</code> I have soimething like this: </p>
  
  <pre><code>package foo
  const (
     OneMoreType agepack.EventType = 100 + iota
  )
  </code></pre>
  
  <p>How can I generate stringer with values from all packages?</p>