code: func (r *Router) FilterPath(path string, filter http.HandlerFunc) {
  	pattern := path
  	pattern = strings.Replace(pattern, "*", "(.+)", -1)
  	pattern = strings.Replace(pattern, "**", "([^/]+)", -1)
  	regex := regexp.MustCompile(pattern)
  	r.Filter(func(w http.ResponseWriter, req *http.Request) {
  		if regex.MatchString(req.URL.Path) { filter(w, req) }
  	})
  }
docs: // FilterPath adds the middleware filter iff the path matches the request.