[Beltalowda]

> However, the issue this brings up about structs / types not explicitly declaring which interfaces they implement is a real and unaddressed problem, especially in large codebases. The only tool that I'm aware of that finds implementations is GoLand, at steep JetBrains prices.

Alan Donovan's guru tool could do this, but it kind of broke with modules and it was never updated and deprecated in favour of gopls. I don't know if gopls added this yet (I never really found a use for it).

I don't think it's very hard to write a tool for this though; parsing Go code is fairly easy and the stdlib provides a decent API for it. I think you could have a functional tool in a day if you wanted to, although without any caching it might be a little bit slow on larger code bases.