当上下文变量超出golang的范围时，Context.Done（）是否会解除阻止？

Question

Will context.Done() unblock when a context variable goes out of scope and cancel is not explicitly called?

Let's say I have the following code:

func DoStuff() {
    ctx, _ := context.WithCancel(context.Background())
    go DoWork(ctx)
    return
}

Will ctx.Done() unblock in DoWork after the return in DoStuff()?

I found this thread, https://groups.google.com/forum/#!topic/golang-nuts/BbvTlaQwhjw, where the person asking how to use Context.Done() claims that context.Done() will unblock when the context variable leaves scope but no one validated this, and I didn't see anything in the docs.

Answer 1

No, it doesn't cancel automatically when the context leaves scope. Typically one calls defer cancel() (using the callback from ctx.WithCancel()) oneself to make sure that the context is cancelled.

https://blog.golang.org/context provides a good overview of how to use contexts correctly (including the defer pattern above). Also, the source code https://golang.org/src/context/context.go is quite readable and you can see there's no magic that would provide automatic cancellation.