Consider moving to another thread locals library

[andrewshadura]

The https://github.com/jtolio/gls module hasn’t been updated in the last 6 years. A currently maintained module, https://github.com/timandy/routine, seems like a more modern replacement.

Please consider moving to it. I tried looking into it myself, but my Go skills are insufficient.

[riannucci]

Is there an underlying bug you're encountering here?

The GLS library very specifically does not rely on the "unsafe" module, while the library you linked to does, which I think will make it unsuitable as a dependency for this project.

(GLS also has at least an order of magnitude less code than routine. Don't confuse "small and stable" with "out of date" :))

Aside: I think really the better thing to do in this modern age is to stop using "goroutine local storage" altogether.
The next evolution of goconvey should rely entirely on explicit context passing instead - hiding the test context in a global variable just ends up causing confusion and bugs :/... Unfortunately such a change will be backwards incompatible which is why I haven't implemented it here.