net/http: Add Close method

[guotie]

Please answer these questions before submitting your issue. Thanks!

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

1.7

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

Linux

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

What did you expect to see?

Add Close method to net/http package to close the http server.

What did you see instead?

[mvdan]

You mean #4674?

[bradfitz]

Yeah, duplicate.