custom error type adding some extras over standard error interface

errors.go

 type customError struct {
 	statusCode  int
 	description string
 	details     interface{}
 }
 
 type CustomError interface {
 	error
 	StatusCode() int
 	Details() interface{}
 	WithStatus(int) CustomError
 	WithDetails(interface{}) CustomError
 }
 
 func New(description string) CustomError {
 	return customError{description: description}
 }
 
 func (err customError) Error() string {
 	return err.description
 }
 
 func (err customError) StatusCode() int {
 	return err.statusCode
 }
 
 func (err customError) Details() interface{} {
 	return err.Details
 }
 
 func (err customError) WithStatus(statusCode int) CustomError {
 	err.statusCode = statusCode
 	return err
 }
 
 func (err customError) WithDetails(details interface{}) CustomError {
 	err.details = details
 	return err
 }
 
 func (err *customError) MarshalJSON() ([]byte, error) {
 	res := struct {
 		StatusCode  int         `json:"status_code"`
 		Description string      `json:"description"`
 		Details     interface{} `json:"details,omitempty"`
 	}{
 		err.statusCode,
 		err.description,
 		err.details,
 	}
 
 	return json.Marshal(res)
 }