code: func (js *Js) GetTicket() (ticketStr string, err error) {
  	js.GetJsAPITicketLock().Lock()
  	defer js.GetJsAPITicketLock().Unlock()
  
  	//先从cache中取
  	jsAPITicketCacheKey := fmt.Sprintf("jsapi_ticket_%s", js.AppID)
  	val := js.Cache.Get(jsAPITicketCacheKey)
  	if val != nil {
  		ticketStr = val.(string)
  		return
  	}
  	var ticket resTicket
  	ticket, err = js.getTicketFromServer()
  	if err != nil {
  		return
  	}
  	ticketStr = ticket.Ticket
  	return
  }
docs: //GetTicket 获取jsapi_ticket