How to configure application to be available subdomain cookie?

Question

I need to share session cookie between main domain and all subdomains. I have two nodejs services based on expressjs framework:

// example.local

    ...
    app.use(session({
       cookie: {
          domain: "example.local"
       }
       , key: 'sid'
       , secret: '[my secret]'
       , saveUninitialized: true
       , resave: true
       , store: new RedisStore({
          host: 'localhost',
          port: 6379
       })
    })); 

// blog.example.local

    ...
    app.use(session({
       // what should I write here? <---------
    })); 

So my question is what should I write in session configuration of blog.example.local to get access to existing cookie of example.local?

EDIT: as @yeiniel suggest, I should just use the same config for blog.example.local like the following:

// blog.example.local

    ...
    app.use(session({
       cookie: {
          domain: "example.local"
       }
       , key: 'sid'
       , secret: '[my secret]'
       , saveUninitialized: true
       , resave: true
       , store: new RedisStore({
          host: 'localhost',
          port: 6379
       })
    })); 

Is it enough or I may optimize it?

Answer 1

Basically you need two things: Use the same settings on all servers (not just cookie settings but all the session settings included the store) and ensure cookie domain configuration point to the common domain between the sites.