code: func URLHandler(name string) func(next http.Handler) http.Handler {
  	return func(next http.Handler) http.Handler {
  		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  			l := FromContext(r.Context())
  			l.SetField(name, r.URL.String())
  			next.ServeHTTP(w, r)
  		})
  	}
  }
docs: // URLHandler returns a handler setting the request's URL as a field
  // to the current context's logger using the passed name as field name.