code: func newAWSIPs(host string, updateFrequency time.Duration, awsRegion []string) *awsIPs {
  	ips := &awsIPs{
  		host:            host,
  		updateFrequency: updateFrequency,
  		awsRegion:       awsRegion,
  		updaterStopChan: make(chan bool),
  	}
  	if err := ips.tryUpdate(); err != nil {
  		dcontext.GetLogger(context.Background()).WithError(err).Warn("failed to update AWS IP")
  	}
  	go ips.updater()
  	return ips
  }
docs: // newAWSIPs returns a New awsIP object.
  // If awsRegion is `nil`, it accepts any region. Otherwise, it only allow the regions specified