There are two things I think you could have as implict in Go - error values, and contexts.

Just pass along two hidden variables for both in parameters and returns, and would anything really change that the compiler wouldn't be able to follow?

i.e. most functions return errors, so there should always be an implicit error return possible even if I don't use it. Let the compiler figure out if it needs to generate code for it.

And same story for contexts: why shouldn't a Go program be a giant context tree? If a branch genuinely doesn't ever use it, the compiler should be able to just knock the code out.