code: func (s *Server) Options(w http.ResponseWriter, req *http.Request) {
  	w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
  	w.WriteHeader(http.StatusOK)
  }
docs: // Options responds to the OPTIONS HTTP method by returning a 200 OK response
  // with the "Access-Control-Allow-Headers" header set to "Content-Type"