code: func FileServer(r chi.Router, path string, root http.FileSystem) {
  	if strings.ContainsAny(path, "{}*") {
  		panic("FileServer does not permit URL parameters.")
  	}
  
  	fs := http.StripPrefix(path, http.FileServer(root))
  
  	if path != "/" && path[len(path)-1] != '/' {
  		r.Get(path, http.RedirectHandler(path+"/", 301).ServeHTTP)
  		path += "/"
  	}
  	path += "*"
  
  	r.Get(path, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  		fs.ServeHTTP(w, r)
  	}))
  }
docs: // FileServer conveniently sets up a http.FileServer handler to serve
  // static files from a http.FileSystem.