How to pass authentication token to websocket call

[apurvk]

I am creating a simple mashup and it generates below config -- 

var config = {
host: window.location.hostname,
prefix: prefix,
port: window.location.port,
isSecure: window.location.protocol === "https:"
};

This is then used to make websocket calls , like https://<host>:<port>/<prefix>/app/engineData?reloadUri=....

I am exposing the dashboard through a different domain. I need to authenticate separately and pass a 'token' to this websocket call.

Like https://<host>:<port>/<prefix>/app/engineData?reloadUri=....&token=<TOKEN>

How to configure the config options to pass this token in every websocket call?

This question is for Qlik Sense enterprise edition.