It has a few bells and whistle and there is some work behind it, no question. HOWEVER, the fact that it relies entirely on go std lib net/http|http2 package imp

It has a few bells and whistle and there is some work behind it, no question. HOWEVER, the fact that it relies entirely on go std lib net/http|http2 package implementations personally doesn't make it very useful if your developing your application in Go directly. Caddy team didn't code all that network layer, like Nginx or Apache teams did. You don't need Caddy to add let's encrypt to your Go application.