在循环迭代器变量上使用goroutines

Question

I was reading that goroutines on loop iterators often result in the last value in the loop assignment being used for every iteration. E.g. https://github.com/golang/go/wiki/CommonMistakes#using-goroutines-on-loop-iterator-variables

However, does this only happen for closures, e.g. with anonymous functions?

I can't seem to reproduce the issue with this example https://play.golang.org/p/lpZ-yD1mHu

When I use an anonymous function like this, it recreates the issue https://play.golang.org/p/mDa0Z6mUP8

Answer 1

However, is this only a problem for closures, e.g. with anonymous functions?

Yes. The difference between

go speak(c)

and

go func() {
    speak(c)
}()

is, the former calls speak with the value of c in a new goroutine. In the latter one, however, the anonymous function captures not the value of c but the variable c itself (by reference¹) and, at some later point in time, calls speak with whatever value c has at this point in time.

¹: There are no "references" in golang, I'm not sure how this is exactly implemented, but it is as if they reference the original variable.