code: func (c *C) MustPostInt(key string, d int) int {
  	val := c.Request.PostFormValue(key)
  	if val == "" {
  		return d
  	}
  	i, err := strconv.Atoi(val)
  	if err != nil {
  		panic(err.Error())
  	}
  
  	return i
  }
docs: /////////////////////////