code: func (h *DeployHandler) randomZone(region string) string {
  	h.zonesMu.RLock()
  	defer h.zonesMu.RUnlock()
  	zones, ok := h.zones[region]
  	if !ok {
  		return fallbackZone
  	}
  	return region + zones[rand.Intn(len(zones))]
  }
docs: // randomZone picks one of the zone suffixes for region and returns it
  // appended to region, as a fully-qualified zone name.
  // If the given region is invalid, the default Zone is returned instead.