Hello, I am maintaining GoQuic and libquic projects.
GoQuic supports TLS connection and not supporting plain HTTP anymore. That document is outdated. Sorry for that, and I will update it soon.
GoQuic (and libquic) is based on chromium QUIC code, So any protocol changes to chromium code should be applied to GoQuic as well.
We currently supports QUIC version 25 ~ QUIC version 33 and are syncing chromium's QUIC code regularly.
FYI We are using our server implementation (GoQuic reverse proxy) on our production servers (with cronet on client side) and it's working well now. I think it is quiet stable.
GoQuic client should work well, but it is less stable than server implementation.