code: func PeriodicChecker(check Checker, period time.Duration) Checker {
  	u := NewStatusUpdater()
  	go func() {
  		t := time.NewTicker(period)
  		for {
  			<-t.C
  			u.Update(check.Check())
  		}
  	}()
  
  	return u
  }
docs: // PeriodicChecker wraps an updater to provide a periodic checker