Simon Willison’s Weblog

28th May 2019 - Link Blog

gls: Goroutine local storage (via) Go doesn't provide a mechanism for having "goroutine local" variables (like threadlocals in Python but for goroutines), and the structure of the language makes it really hard to get something working. JT Olio figured out a truly legendary hack: Go's introspection lets you see the current stack, so he figured out a way to encode a base-16 identifer tag into the call order of 16 special nested functions.

I particularly like the "What are people saying?" section of the README:

"Wow, that's horrifying."

"This is the most terrible thing I have seen in a very long time."

"Where is it getting a context from? Is this serializing all the requests? What the heck is the client being bound to? What are these tags? Why does he need callers? Oh god no. No no no."