Fingerprint authentication in real world



I’m trying to find a way to use a fingerprint authentication in real world.
All examples I’m seeing over internet it’s just using fingerprint to access another page…

To do all tests I’m using plugin , it works great but I was a little but disappointed about something :
When the phone successfully recognize my finger, the plugin return a sort of ID, for example : x7D6…
If tap again on the authentication button and use same finger, plugin return another ID : a8c4…

So my first goal to save the first saved ID in a DB and reuse it later to authenticate an user cannot work…
Now, if it’s possible, I need to :

User open app, login with regular nickname and password, if phone is compatible, ask user if he want to use fingerprint. If user accept, app ask to verify fingerprint, user do it, it’s a success and plugin return the ID. The ID is saved and linked to his account.
User decide to disconnect from his account. And this time he choose fingerprint authentication, app ask him to verify fingerprint, user do, it’s success, and plugin return the ID, if ID is link to an account (his own), connect him to his account.

It is possible to do something like this, or it’s unsecure ?
Another way to do this ?

Thanks for your help, because now I don’t know what’s the interest of using fingerprint authentication in a real app ?