In my quest to build an #ActivityPub based simple, no-frills bulletin board / forum system, I've gone ahead and pushed up my work-in-progress #golang ActivityPub single server framework: apcore. It has no README (yet) and still has a lot left TODO.
https://github.com/go-fed/apcore
I hope to use it in the future to launch multiple small ActivityPub applications leveraging common serving, storing, and moderation features. But new #ActivityStreams vocabulary can be readily innovated upon.