net: clarify documentation on net.ListenConfig.Listen and related calls w.r.t. context

What version of Go are you using (go version)?

go version go1.11.1 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64" GOOS="linux"

What did you do?

I created a net.ListenConfig.Listen(cancelableCtx, "unix", "/path/to/socket") to create a Unix socket, and called Accept on said listener.

What did you expect to see?

I expected canceling the context to cancel the Accept.

What did you see instead?

The Accept was not canceled.

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So maybe my expectation was wrong. I reasoned "Why else would there be a context there if not to cancel (or time out) the Accept calls?". But clearly not.

I asked on the #general channel in the Gophers Slack and was reminded that Dial, for example, specifically says that once Dial completes, the context it's given doesn't affect the connection, and that probably Listen & Accept were similar. That does appear to be the case.

So, for folks like me that are not terribly familiar with network or socket programming, would it be possible to note in the Listen & Accept docs that the given context doesn't affect the later Accept? And maybe even what the Listen context actually does; it wasn't 100% clear to me.

Thanks.