code: func (hc HostnameCheck) Check() (warnings, errorList []error) {
  	klog.V(1).Infoln("checking whether the given node name is reachable using net.LookupHost")
  	errorList = []error{}
  	warnings = []error{}
  	addr, err := net.LookupHost(hc.nodeName)
  	if addr == nil {
  		warnings = append(warnings, errors.Errorf("hostname \"%s\" could not be reached", hc.nodeName))
  	}
  	if err != nil {
  		warnings = append(warnings, errors.Wrapf(err, "hostname \"%s\"", hc.nodeName))
  	}
  	return warnings, errorList
  }
docs: // Check validates if hostname match dns sub domain regex.