How to pass data to appcomponent page from other page

I’m using ionic 4.

i defined sidemenu in app.component.html and i want to pass username (this data comes from api in login.page.ts) to sidemenu after login.
i’m able to store username value in some variable in login.page.ts, but i want to pass this value to app.component.html.

This should be keep within a service module. This module would contain all the communication with the api and the user status. There should be several good tutorials on how to set this up.