code: func registerVars(r *http.Request, vars map[string]string) {
  	parts, i := make([]string, len(vars)), 0
  	for key, value := range vars {
  		parts[i] = url.QueryEscape(":"+key) + "=" + url.QueryEscape(value)
  		i++
  	}
  	q := strings.Join(parts, "&")
  	if r.URL.RawQuery == "" {
  		r.URL.RawQuery = q
  	} else {
  		r.URL.RawQuery += "&" + q
  	}
  }
docs: // registerVars adds the matched route variables to the URL query.