For other fun surprises that are rather obvious from the implementation but still surprise people quite regularly: wait until you see how much slower context ke

For other fun surprises that are rather obvious from the implementation but still surprise people quite regularly: wait until you see how much slower context keys are when compared to thread locals, particularly since it's normal for contexts to contain MANY layers (as opposed to errors, which are frequently* returned without wrapping at almost any level). It's a glorified linked-list lookup, and it re-walks the whole path every time. But for both contexts and errors: imo the tradeoff is overwhelmingly in favor of wrapping more, not less, in the vast majority of code. Context is useful and standard for many things, and wrapped errors carry a lot more useful information, and both of those are absolutely crucial for healthy interop with other code. Performance sensitive stuff can do whatever it needs, these are obviously terrible choices there so just don't even consider it. * but not always! and it may change with time. Still, my contexts are regularly 10+ layers deep while my errors are rarely more than one or two.