package errhttp type NotFound interface { ClientError NotFound () } type internalNotFound struct { err error } func NotFoundWrap(err error) error { return internalNotFound { err:err, } } func (receiver internalNotFound ) Error() string { return receiver.err.Error() } func (receiver internalNotFound ) Err() error { return receiver.err } func (internalNotFound ) ClientError() { // Nothing here. } func (internalNotFound ) NotFound() { // Nothing here. } func (receiver internalNotFound) Unwrap() error { return receiver.err }