First of all, the best way to site-search is to use Google. Seriously, why are you hurting yourself?

Second of all, I can't understand the situation where this would come up. Obviously in normal circumstances it doesn't even come up.

* You wanna search all forums at once? Use Google (or DDG, or the shitty one).

* There's a Go-specific forum? So obviously you don't need to specify Go in the search.

* The forum isn't about Go? Then why are you searching there?

So for your complaint to make sense, you need to have a particular forum you want to limit your searches to, AND you don't want to use Google with site:stupidforum.com, AND the forum covers multiple programming languages, AND the forum doesn't have a tagging system to tag go-lang posts (like basically every programming forum does), AND it has this problem I've never heard of where it rejects 2-letter words?

I'm really trying to avoid just saying "bullshit", but I think you're bullshitting us. Name one such forum.

Again, as I asked in the grandparent comment, name one search engine where you, or anyone you know personally, has had this problem.

I am not surprised that shitty message board search functionality was not considered when naming the language (How do you even search for "C" with such a system?)