code: func Tags(c context.Context) []string {
  	if tags, ok := c.Value(&clockTagKey).([]string); ok && len(tags) > 0 {
  		tclone := make([]string, len(tags))
  		copy(tclone, tags)
  		return tclone
  	}
  	return nil
  }
docs: // Tags returns a copy of the set of tags in the current Context.