code: func AddServiceFields(rw http.ResponseWriter, req *http.Request, next http.Handler, data *LogData) {
  	data.Core[ServiceURL] = req.URL // note that this is *not* the original incoming URL
  	data.Core[ServiceAddr] = req.URL.Host
  
  	next.ServeHTTP(rw, req)
  
  }
docs: // AddServiceFields add service fields