function blah() {
   sub.unsubscribe();
   sub.subscribe("a");
   sub.subscribe("b");
}

var redis = require('redis')

const subscribe = redis.createClient({
    host: 'localhost',
    port: 6379
})
subscribe.psubscribe(`user:chat:*`)

subscribe.on('pmessage', function(pattern, channel, message) {
    console.log(channel, message, pattern)
    // Write Your Awesome Code here.
})