code: func AdminOnly(next http.Handler) http.Handler {
  	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  		isAdmin, ok := r.Context().Value("acl.admin").(bool)
  		if !ok || !isAdmin {
  			http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
  			return
  		}
  		next.ServeHTTP(w, r)
  	})
  }
docs: // AdminOnly middleware restricts access to just administrators.