Related: #3778

Reference: http://nginx.org/en/docs/http/ngx_http_upstream_module.html#hash

Reference: https://doc.traefik.io/traefik/v2.0/

…3776)

See also: https://stackoverflow.com/questions/52760509/typescript-returntype-of-overloaded-function/52760599#52760599

Related: #3770

In Socket.IO v2, the Socket query option was appended to the namespace
in the CONNECT packet:

{
  type: 0,
  nsp: "/my-namespace?abc=123"
}

Note: the "query" option on the client-side (v2) will be found in the
"auth" attribute on the server-side:

```
// client-side
const socket = io("/nsp1", {
  query: {
    abc: 123
  }
});
socket.query = { abc: 456 };

// server-side
const io = require("socket.io")(httpServer, {
  allowEIO3: true // enable compatibility mode
});

io.of("/nsp1").on("connection", (socket) => {
  console.log(socket.handshake.auth); // { abc: 456 } (the Socket query)
  console.log(socket.handshake.query.abc); // 123 (the Manager query)
});

More information here: https://socket.io/docs/v3/migrating-from-2-x-to-3-0/#Add-a-clear-distinction-between-the-Manager-query-option-and-the-Socket-query-option

Related: #3791

Diff: 3.1.0...3.1.1