I am quite interested in go-i2p myself. How usable is it?
As for HORNET, I saw a minor Go impl of the ideas [0] along w/ a tiny mailing list post [1]. While it does appear to be made for backbone network devices, I believe the concept of onion routing w/ basically multi-hop TLS can be done in layer 7. I think the one thing missing is an implementation people can use and depend on (definitely outside of my present abilities).