code: func (h ddlResignOwnerHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
  	if req.Method != http.MethodPost {
  		writeError(w, errors.Errorf("This api only support POST method."))
  		return
  	}
  
  	err := h.resignDDLOwner()
  	if err != nil {
  		log.Error(err)
  		writeError(w, err)
  		return
  	}
  
  	writeData(w, "success!")
  }
docs: // ServeHTTP handles request of resigning ddl owner.