Adjust forward auth to avoid connection leak

[wdhongtw]

What does this PR do?

This MR provides a minor bug fix for forward auth middleware implementation.

During the sub-request of forward auth process, If error happens on io.ReadAll(forwardResponse.Body), current implement won't close the body, the underline http connection can not be reuse for next request, and results in connection leak in HTTP 1.1 environment.

The only change in this MR is to register the defer statement earlier, covering all possible execution path.

Although it’s unlikely for a working connection to return error on body read, it’s still a good practice to defer body.Close() immediately after client.Do if it does not return error.

See also:

• net/http document: https://pkg.go.dev/net/http
• persistConn and bodyEOFSignal implementation: https://github.com/golang/go/blob/master/src/net/http/transport.go

Motivation

It's not a serious bug, just nitpicking some implementation details. :D

More

• Added/updated tests
• Added/updated documentation

Additional Notes

I grep the code base with client.Do usage, another issue I found is in integration/try/try.go.
Since that package is only used in test, it’s should be ok to keep it untouched. :D

[rtribotte]

Hello @wdhongtw,

Thanks for this contribution!

Can you please rebase the PR on the v2.10 branch?
While we think it is worth doing this change as a better pattern, we are unsure that the problem could really happen.
Nonetheless, this is more of a bug fix and hence it should be merged on the current v2.10.

[wdhongtw]

@rtribotte No problem :D

[nmengin]

LGTM thanks 👍

[rtribotte]

Thanks!