net/http: describe where multiple response.WriteHeader calls occur

[dsnet]

I see this in an HTTP server log:

server.go:2315: http: multiple response.WriteHeader calls

Written by the http package here.

It would be nice if it described file+line of the first non-http package function that caused WriteHeader to be called so that it's easier to find the offending code.

\cc @bradfitz

[siadat]

I can work on this if it is okay.

Regarding the implementation, would it be okay to use runtime.Callers here, and find the first function whose name does not start with "net/http."?

[bradfitz]

@siadat, sounds like it could work.

As long as you only do that work when we're already spamming logs, and not for all WriteHeader calls.

[gopherbot]

CL https://golang.org/cl/36096 mentions this issue.

[odeke-em]

Hello there @siadat, Go1.11 is active right now and @danp pinged you on the CL, please let us know if you'll be carrying on with the CL, if you are busy, no worries, we can work on it.

[siadat]

Hi @odeke-em, thanks for the reminder, I will have a look at it!