proxy.golang.org is served by the same Google-wide serving infrastructure as all Google sites, so whatever's going on here is not specific to proxy.golang.org.

#29125 looks vaguely related. I'm not a net/http expert, but my best guess is that @darsenault has some kind of middlebox that's messing with the connection.

@darsenault here to add a bit of context.

• Problem was present when all potential middleboxes and AV were bypassed and suspended, respectively.

• Problem was still present when attached to a alternate wide open network (phone hotspot tether).

• Problem resolved upon removal of proxy.golang.org fro GOPROXY, keeping all else constant including potential middleboxes and AV.

• All other libraries attempted via go get worked flawlessly, including several dozen from the Benthos (benthos.dev) build process and random packages selected from Awesome Go. The only package impacted was github.com/microcosm-cc/bluemonday when GOPROXY contained proxy.golang.org

Sorry, I have no idea what could be going wrong. HTTP/2-level concerns are handled by Google-wide serving infrastructure, which is completely oblivious to what module you're requesting. As far as I know it should be literally impossible for proxy.golang.org to cause this problem. And we've never had a report like this before.

It seems like you checked all the right things, but it still sounds more like something interfering with the connection than a server-side bug. If you want to debug further, I'd suggest getting a pcap.

Or maybe GODEBUG=http2debug=2, from the bug I linked.

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)