Proxying WebSocket connections in Go

Golang’s net/http package provides built-in support for http_proxy and https_proxy. This is awesome when developing apps locally, because one can use a tool like Proxyman to watch the traffic.

In a side project, I needed to use a WebSocket client. I used github.com/gobwas/ws and while proxy is not supported out of the box, it was very easy to add using golang.org/x/net/proxy which supports SOCKS5.

Here’s the snippet:

package main

import (
	"context"
	"fmt"

	"github.com/gobwas/ws"
	"golang.org/x/net/proxy"
)

func main() {
	dialer := ws.Dialer{
		NetDial: proxy.Dial,
	}

	conn, reader, _, err := dialer.Dial(context.Background(), "wss://example.org/ws"))
	if err != nil {
		fmt.Fatal("connect to WebSocket server", err)
	}

	// ...
}

Make sure to run your app with ALL_PROXY env var (all_proxy will work too):

ALL_PROXY=socks5://127.0.0.1:8889 go run main.go

Finally, you may need to enable SOCKS5 proxy in your proxy app. In Proxyman, it’s disabled by default and can be enabled by going into Tools › Proxy Settings › SOCKS Proxy Settings.... A popup window will appear where you can toggle the proxy and configure the port.

If you don’t want to pass an env var, proxy.FromURL is your friend.