In this case, this is a library for Go, not a standalone program, so it seems worthwhile to include the language in the description. If there's something technical about Go that makes pure-go implementations of things interesting it's that it's uncommon/frowned upon to use cgo to import c dependencies whereas in python/ruby/etc you can trivially wrap a C library for many things and call it a day.

Also, you mention you don't see similar posts for other languages, however, similar complaints are constantly lodged against Rust posts, maybe even more so than Go. A recent comment in one of those threads also mentioned similar musings were common against python earlier in its history.

Regardless, Go and Rust are popular languages on HN right now because they're new and interesting and being used to build interesting new software. In practice, other older languages are more popular for work, but as the library ecosystems improve, maybe that will change or maybe it won't.