Assigning WebSocket and net.Socket with unique id [Typescriprt]

I aspire to assign Websockets and net.Sockets with unique identifiers, so when a message is received, the client is identified by the identifier attached to the socket.

Previous research:

For Websocket:

According to this and this, the following is requires:

const app = express();
const server = http.createServer(app);
const wss = new WebSocket.Server({ server });
wss.on('connection', (ws) => {
   ws.id = uuid.v4(); // This is the relevant line of code
   ws.on('message', (msg: string) => {
   ...
   }
});

For net.Socket:

Quite the same - according to this, the following is required:

var server = net.createServer();

server.on('connection', function(conn) {
    conn.id = uuid.v4(); // This is the relevant line of code
    conn.on('data', function(data) {
    ...
    });
});

The problem

The error "Property 'id' does not exist on type 'WebSocket' [or 'Socket' accordingly]" during compilation. This explains why.

Optional Solution #1: Cast to any

The update net.Socket code will be:

var server = net.createServer();

server.on('connection', function(conn) {
    (conn as any).id = uuid.v4();
    conn.on('data', function(data) {
        console.log('Session id:' + (conn as any).id);
    });
});

The problem: It doesn't seem like good practice to me. I don't have references for why except for a hunch for now.

Optional Solution #2: Use a local variable [seems like a better option]

The update net.Socket code will be:

var server = net.createServer();

server.on('connection', function(conn) {
    const id: string = uuid.v4();
    conn.on('data', function(data) {
        console.log('Session id:' + id);
    });
});

After some experiencing, it seems to work properly.

So - the questions:

1. In optional solution #2: is it guaranteed that the id variable will always be available in this scope? In other words: is this solution valid? for both net.Socket & Websocket? Or is there something that I'm missing?
2. In general: Is there additional identifiers (perhaps built in identifiers in WebSocket and net.Socket) that can be used instead?

[Typescript version: 3.2.4].

from Assigning WebSocket and net.Socket with unique id [Typescriprt]