code: func (c *Controller) CalcExample(ctx *gin.Context) {
  	val1, err := strconv.Atoi(ctx.Query("val1"))
  	if err != nil {
  		httputil.NewError(ctx, http.StatusBadRequest, err)
  		return
  	}
  	val2, err := strconv.Atoi(ctx.Query("val2"))
  	if err != nil {
  		httputil.NewError(ctx, http.StatusBadRequest, err)
  		return
  	}
  	ans := val1 + val2
  	ctx.String(http.StatusOK, "%d", ans)
  }
docs: // CalcExample godoc
  // @Summary calc example
  // @Description plus
  // @Tags example
  // @Accept json
  // @Produce json
  // @Param val1 query int true "used for calc"
  // @Param val2 query int true "used for calc"
  // @Success 200 {integer} integer "answer"
  // @Failure 400 {string} string "ok"
  // @Failure 404 {string} string "ok"
  // @Failure 500 {string} string "ok"
  // @Router /examples/calc [get]