string.go
func StringMarshalJSON(data interface{}, indent string) string {
	buffer, err := json.MarshalIndent(data, "", indent)
	if err != nil {
		return ""
	}
	return string(buffer)
}
func StringMarshalJSON(data interface{}, indent string) string {
	buffer, err := json.MarshalIndent(data, "", indent)
	if err != nil {
		return ""
	}
	return string(buffer)
}
// StringMarshalJSON marshals data to an indented string.