It's in progress. Algernon is an open source project where I am the main contributor, and I develop Algernon in my spare time. Pull requests are welcome.
I pretty much followed the instructions here: https://godoc.org/golang.org/x/crypto/acme/autocert
edit, better here: https://blog.kowalczyk.info/article/Jl3G/https-for-free-in-g...
I didn't believe it could be that simple, but it worked first time and has proven really robust.
Edit: Taken from certmagic docs
Instead of:
// plaintext HTTP, gross
http.ListenAndServe(":80", mux)
Use CertMagic:
// encrypted HTTPS with HTTP->HTTPS redirects - yay!
certmagic.HTTPS([]string{"example.com"}, mux)