errors.go
func NewSystemError(code SystemErrCode, msg string, args ...interface{}) error {
	return SystemError{code: code, msg: fmt.Sprintf(msg, args...)}
}
func NewSystemError(code SystemErrCode, msg string, args ...interface{}) error {
	return SystemError{code: code, msg: fmt.Sprintf(msg, args...)}
}
// NewSystemError defines a new SystemError with a code and message