code: func MyHostname() string {
  	myHostnameOnce.Do(func() {
  		var err error
  		myHostname, err = os.Hostname()
  		if err != nil {
  			log.Fatal(err)
  		}
  	})
  	return myHostname
  }
docs: // Like os.Hostname but caches first successful result, making it cheap to call it
  // over and over.
  // It will also crash whole process if fetching Hostname fails!