How to initialize socket with a secure connection?

[mkhoussid]

Currently, I have the following:

// client
. . .
import { io } from 'socket.io-client';
. . .
const socket = io('https://my_domain.com', {
		reconnectionDelay: 1000,
		reconnection: true,
		reconnectionAttemps: 10,
		transports: ['websocket', 'polling', 'flashsocket'],
		agent: false,
		upgrade: true,
		secure: process.env.NODE_ENV !== 'development',
		rejectUnauthorized: false,
		query: { userId: user.id },
});

// server
. . .
import fastifySocketIo from 'fastify-socket.io';
. . .
app.register(fastifySocketIo, {
	pingInterval: 10000,
	pingTimeout: 5000,
	cookie: false,
});
. . .

Locally everything works just fine, but when NODE_ENV is set to production, a connection can't be made. What am I doing wrong here?