code: func (v *IntString) UnmarshalJSON(raw []byte) error {
  	if raw == nil || bytes.Equal(raw, []byte(`"null"`)) || bytes.Equal(raw, []byte(`""`)) {
  		return nil
  	}
  
  	strVal := string(raw)
  	if rune(raw[0]) == '"' {
  		strVal = strings.Trim(strVal, `"`)
  	}
  
  	i, err := strconv.ParseInt(strVal, 10, 64)
  	if err != nil {
  		return err
  	}
  
  	v.Value = i
  	v.Valid = true
  
  	return nil
  }
docs: // UnmarshalJSON implements custom unmarshalling for IntString type