code: func Dedupe(next log.Logger, repeat time.Duration) *Deduper {
  	d := &Deduper{
  		next:   next,
  		repeat: repeat,
  		quit:   make(chan struct{}),
  		seen:   map[string]time.Time{},
  	}
  	go d.run()
  	return d
  }
docs: // Dedupe log lines to next, only repeating every repeat duration.