code: func Jitter(duration time.Duration, maxFactor float64) time.Duration {
  	if maxFactor <= 0.0 {
  		maxFactor = 1.0
  	}
  	wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
  	return wait
  }
docs: // Jitter returns a time.Duration between duration and duration + maxFactor *
  // duration.
  //
  // This allows clients to avoid converging on periodic behavior. If maxFactor
  // is 0.0, a suggested default value will be chosen.