code: func jitter(i int) time.Duration {
  	ms := i * 1000
  
  	maxJitter := ms / 3
  
  	// ms ± rand
  	ms += random.Intn(2*maxJitter) - maxJitter
  
  	// a jitter of 0 messes up the time.Tick chan
  	if ms <= 0 {
  		ms = 1
  	}
  
  	return time.Duration(ms) * time.Millisecond
  }
docs: // jitter keeps the +/- 0-33% logic in one place