Perhaps, but other languages that look a lot like Go with these additions (e.g. OCaml) have not gained much popularity, despite getting much more love on forums

Perhaps, but other languages that look a lot like Go with these additions (e.g. OCaml) have not gained much popularity, despite getting much more love on forums like HN. It's important to remember that the people expressing strong opinions about sum types on the internet are a tiny and non-representative fraction of working programmers.