Configuring express session store to work across subdomain

SessionSubdomains.js

app.use(express.cookieParser());
app.use(express.session({
  secret: 'MySecret', //Should be the same across all the apps that share the same sessions.
  store: Bla, //Init your store here
  cookie: {domain: '.mydomain.com'} //The point in front here is important so that the same sessions work across all sub-domains.
}));