net/http: add examples/comments for Server.Shutdown

[amkgo]

Please answer these questions before submitting your issue. Thanks!

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

Go 1.8

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

amd64(windows 7 & Ubuntu 16.04)

What did you do?

https://play.golang.org/p/Akv3se9kkZ

What did you expect to see?

Go file server shutdown after download the file or timeout is reached

What did you see instead?

File server shutdown immediately

This issue is related to #19541.

The Shutdown function may need some comments or examples to warn gophers to keep ListenAndServe running until it finished.

Or if possible, make Shutdown communicate with ListenAndServe internally to make https://play.golang.org/p/Akv3se9kkZ works.

Thanks,
Andrew

[pierrre]

I agree, ListenAndServe() should block until Shutdown() returns.

I was trying to implement a graceful shutdown in my app.
I think I'll move the Shutdown() call to my "main/blocking execution path".

[loopthrough]

I looked a bit into this one and made a small change to embed the synchronisation of Shutdown() and Serve() in the net/http itself instead of expecting to synchronise them through main.

Proposal for the change.
https://go-review.googlesource.com/c/45094

I am looking as well into testing it properly, but wanted to check if this approach is reasonable to move forward with.

[fraenkel]

None of these prevent someone calling Serve during a Shutdown or even after Shutdown. The fix seems to handle a very specific use of Server and not the case where you have potentially multiple listeners.

[amkgo]

I've used Nginx before and it can be shutdown or restart gracefully. Maybe we can get some ideas from it.

[gopherbot]

CL https://golang.org/cl/48869 mentions this issue.

[smcquay]

@amkgo I added a chan communication before exit and after shutdown:

https://play.golang.org/p/wnUgZfHh2W

Does that not behave as expected?

[mrwonko]

I think this is related to #20239