pass SubProtocols to Upgrade

[mrkmrtns]

Problem

We have problem that SubProtocols are not known beforehand and are rather dynamic. Therefore we need capability to specify support subprotocols for every websocket connection.

I made it by adding next to Upgrade function UpgradeWithOptions.

https://github.com/lxzan/gws/compare/master...mrkmrtns:gws:upgradewithoptions You can check it out here, if it suits for You then I can prepare PR.

UpgradeOptions struct can be extended in future for any other overwrites/opts - currently added there only SubProtocols for our need.

Any questions/recommendations are welcome.

[lxzan]

What usage scenarios require a dynamic Sec-WebSocket-Protocol ?

[mrkmrtns]

Sec-WebSocket-Protocol is used for packing into there also session credentials - it allows us to check at time connection is created if You are allowed to establish it in first place. We do not want to allow establish connection at all if You are not allowed to.

Another option would be to use query parameters for that, but for obvious reasons it's not good idea to set it that way. Afaik using SubProtocols is the only way You can send it in header from browser.

So we can say there is practically infinite numbers of those, one per valid session.

[lxzan]

The original was to use sub-protocols for authentication, not a recommended practice, but it works.

This can be achieved without modifying the gws source code

• client

let ws = new WebSocket($addr, ['gws', $token])

• server

upgrader := gws.NewUpgrader(&Handler{}, &gws.ServerOption{
    SubProtocols: []string{"gws"},
})

The server can then get the token from the request header

[mrkmrtns]

When sending "multiple" then it indeed works, although with just token would be nicer imo. As I see You do not want to add overwrite option - then can workaround as You suggested.