code: func GetAPIServerProbeAddress(endpoint *kubeadmapi.APIEndpoint) string {
  	// In the case of a self-hosted deployment, the initial host on which kubeadm --init is run,
  	// will generate a DaemonSet with a nodeSelector such that all nodes with the label
  	// node-role.kubernetes.io/master='' will have the API server deployed to it. Since the init
  	// is run only once on an initial host, the API advertise address will be invalid for any
  	// future hosts that do not have the same address. Furthermore, since liveness and readiness
  	// probes do not support the Downward API we cannot dynamically set the advertise address to
  	// the node's IP. The only option then is to use localhost.
  	if endpoint != nil && endpoint.AdvertiseAddress != "" {
  		return endpoint.AdvertiseAddress
  	}
  
  	return "127.0.0.1"
  }
docs: // GetAPIServerProbeAddress returns the probe address for the API server