Given that preface, I was really expecting that link to be a grepping tool rewritten in golang or something, or perhaps customised for markdown to weigh matches in "# heading title"s heavier for example

Here's a rust one: https://github.com/BeaconBay/ck

I haven't used it extensively, but semantic grep alone was kind of worth it.

Right, I should have said Rust. Golang is so 2017!