code: func (b *Box) HasDir(name string) bool {
  	oncer.Do("packr2/box/HasDir"+b.Name, func() {
  		for _, f := range b.List() {
  			for d := filepath.Dir(f); d != "."; d = filepath.Dir(d) {
  				b.dirs.Store(d, true)
  			}
  		}
  	})
  	if name == "/" {
  		return b.Has("index.html")
  	}
  	_, ok := b.dirs.Load(name)
  	return ok
  }
docs: // HasDir returns true if the directory exists in the box