It was definitely 1. There were ways to demonstrate the issue without involving goroutines, such as by creating a list of closures in a loop, one at each iterat

It was definitely 1. There were ways to demonstrate the issue without involving goroutines, such as by creating a list of closures in a loop, one at each iteration, and then invoking them synchronously after the loop exits. They would all have the same (in this case, final) value of i.