If there is a link, I'd say it's devops —except cockroach and caddy of course.

Go is a very useful language for this space, as it's easy (we aren't developers after all), it's safe, fast, compiles to a single binary, easy cross-compile support, software written in it tends to be robust, great basic library, etc.

Only a minority of those projects have anything to do with containers.

I don't know if "echo system" is a deliberate mistake, but i like it!