> `ctx.Value` is an `any -> any`

It did not have to be this way, this is a shortcoming of Go itself. Generic interfaces makes things a bit better, but Go designers chose that dumb typing at first place. The std lib is full of interface {} use iteself.

context itself is an after thought, because people were building thread unsafe leaky code on top of http request with no good way to easily scope variables that would scale concurrently.

I remember the web session lib for instance back then, a hack.

ctx.Value is made for each go routine scoped data, that's the whole point.

If it is an antipattern well, it is an antipattern designed by go designers themselves.