code: func (a *StandardEWMA) Tick() {
  	count := atomic.LoadInt64(&a.uncounted)
  	atomic.AddInt64(&a.uncounted, -count)
  	instantRate := float64(count) / float64(5e9)
  	a.mutex.Lock()
  	defer a.mutex.Unlock()
  	if a.init {
  		a.rate += a.alpha * (instantRate - a.rate)
  	} else {
  		a.init = true
  		a.rate = instantRate
  	}
  }
docs: // Tick ticks the clock to update the moving average.  It assumes it is called
  // every five seconds.