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