[mafredri]

Adds experimental WebSocket over HTTP/2 (RFC 8441 extended CONNECT). It is opt-in on both sides through the new HTTPProtocol field in AcceptOptions and DialOptions. The zero value keeps today's HTTP/1.1 behavior, and on Wasm the field does nothing.

• Server: Accept with HTTPProtocol2 accepts only extended CONNECT, and with HTTPProtocolAny it accepts both. The process must run with GODEBUG=http2xconnect=1, because Go has disabled extended CONNECT by default since Go 1.24 (net/http: do not enable HTTP/2 extended connect by default golang/go#71128). CL 776300 proposes a per-server option instead (net/http: add support for SETTINGS_ENABLE_CONNECT_PROTOCOL golang/go#53208). Over HTTP/2, Accept does not require Sec-WebSocket-Key, because Chrome and Firefox send none (RFC 8441 §5). It answers a key that is present with Sec-WebSocket-Accept, for HTTP/1.1 clients behind proxies such as Envoy.
• Client: Dial with HTTPProtocol2 needs an http.Client that uses golang.org/x/net/http2.Transport, because net/http's own client rejects the :protocol pseudo-header. On Go 1.27 the program must also be built with -tags http2legacy, because x/net's transport otherwise hands requests to net/http. Dial cannot detect whether a transport supports HTTP/2, so the caller chooses the protocol. Dial still sends a key over HTTP/2, for HTTP/1.1 servers behind proxies, and checks Sec-WebSocket-Accept only when the server sends one.

The HTTP/2 tests are in internal/thirdparty/http2, because they import x/net. ci/test.sh runs them with GODEBUG=http2xconnect=0 and with =1, and adds their coverage to the main report. A runnable example is in internal/examples/http2.

Dial now also rejects an HTTP/1.1 handshake response with a ProtoMajor other than 0 or 1 (#550), so an HTTP/3 response is not treated as an upgrade. HTTP/2 benchmarks are not included.

Closes #4

Decision log

• ProtoMajor 0 is accepted: custom RoundTrippers that build the response by hand may leave it unset, and rejecting them would break dials that work today.
• The example and test servers use net/http (Server.Protocols, Go 1.24+), not x/net's ConfigureServer and h2c, which x/net deprecates. The x/net client stays, with //lint:file-ignore SA1019, because net/http has no way to send :protocol yet.
• golang.org/x/net (v0.62.0) and golang.org/x/text (v0.43.0) are bumped in the internal modules to clear govulncheck. Those x/net releases require go 1.26.0, so both internal go directives say 1.26.0.
• Checked on Go 1.27.3: the HTTP/2 suite fails its 3 successful-dial cases without -tags http2legacy and passes with it.

🤖 This PR was created with the help of Coder Agents.

[code-asher]

Very nice 🤌 I messed around with the example as well and it all looks good.

[mtojek]

Amazing skills 👍 👍

Have you tried to establish a connection using other tools? JS possibly?

[code-asher]

Have you tried to establish a connection using other tools? JS possibly?

While I was testing I experimented with connecting to the server example from a JS (Node) client. Here is what I used for anyone interested (needs ws).

const http2 = require("http2")
const { Receiver, Sender } = require("ws")

const client = http2.connect("http://127.0.0.1:8080")

const req = client.request({
 ":method": "CONNECT",
 ":protocol": "websocket",
 ":scheme": "http",
 ":path": "/",
 ":authority": "127.0.0.1",
 "Sec-WebSocket-Key": "AQIDBAUGBwgJCgsMDQ4PEC==",
 "Sec-WebSocket-Version": "13",
})

req.on("response", (headers) => {
 console.log("status:", headers[":status"])
})

req.on("error", (err) => {
 console.log("error:", err)
})

const receiver = new Receiver()
receiver.on("message", (data) => {
 console.log("got message:", data.toString())
})

req.on("data", (chunk) => {
 receiver.write(chunk)
})

setInterval(() => {
 const sender = new Sender(req)
 sender.send("hey", { binary: false, mask: true, fin: true })
}, 1000)

sample output:

status: 200
got message: hey
got message: hey
got message: hey

[Nek-12]

Are there plans to ship this?

[mafredri]

@Nek-12 yes, absolutely! This fell on the back-burner but I will take another look at it next week.

[ybaldus]

@mafredri With go 1.27 x/net/http2 moved into the standard library. It might be worth to relook into the changes. See: https://pkg.go.dev/golang.org/x/net/http2#section-readme

I would be interested in the http2 websocket server. Do you need any help to ship this?