code: func (s *handler) ok(w http.ResponseWriter, val ...interface{}) {
  	w.WriteHeader(http.StatusOK)
  
  	if len(val) == 0 {
  		return
  	}
  
  	err := json.NewEncoder(w).Encode(struct {
  		Value interface{} `json:"value,omitempty"`
  	}{
  		val[0],
  	})
  
  	if err != nil {
  		log.Panic(err)
  	}
  }
docs: // ok responds with http.StatusOK and json encodes val if given.