Sharing a cookie between multiple apps on localhost - node.js

Question

My API (localhost:8080) issues cookies for my frontend (localhost:3000). The cookies domains are set to "NULL" on development mode.
I have another small frontend (localhost:9000) on the side. It will be deployed as a subdomain of the frontend in production, so I shouldn't have issue.
In development, I have found no way to request the API from my small frontend, I have no CORS issues but my API throws 401 because the small frontend isn't sending the cookie. The "Send For" attribute is set to "Any type of connection". The cookie is set to expire in a year. I checked in the browser settings, on both ports the cookie is there with the same settings and content.
On the small frontend I can list the cookies on document.cookie but trying to retrieve any value from the cookie using either
function getCookie(key) {
var keyValue = document.cookie.match('(^|;) ?' + key + '=([^;]*)(;|$)');
return keyValue ? keyValue[2] : null;
}
getCookie('sid');
OR
$.cookie('sid');
Doesn't work.
Setting the cookie domain to NULL doesn't work.
Setting the cookie domain to localhost doesn't do the trick either and it isn't supported by chrome. (see this) It is supported on FF but I have the same issues
I have tried to set the cookies domain to ".app.localhost" and then set in /etc/hosts
127.0.0.1:8080 api.app.localhost
127.0.0.1:9000 app.app.localhost
127.0.0.1:3000 front.app.localhost
But I couldn't access my apps.
I think I missing something big here.
EDIT:
About the /etc/hosts file
After some digging I found out that ports cannot be specified on ips
However, you can set it up this way:
127.0.0.1 api.app.localhost:8080
127.0.0.1 app.app.localhost:3000
127.0.0.1 app2.app.localhost:9000
I can access and login on my app.app.localhost:3000 with the cookie set to .app.localhost, when I go to app.app.localhost:9000 I can see that there is a cookie containing my sessionId setup with .app.localhost as domain and Any kind of connection.
Yet, same issue as explained above.