The beta is now official as well as globally as WhatsApp officially announced fingerprint lock feature. This was made know yesterday being 31th November, 2019 and is now live in all country. With this, Android users can now have the app lock automatically, and unlock only with their fingerprint.
Android users can now choose to lock the app – with their fingerprints as authentication to unlock it thereafter. Users can also choose how much time the app will automatically lock in which options include immediately after closing, after 1 minute, and after 30 minutes. You will also be able to choose whether the content of your messages will be visible in notifications, including the sender of the message.

To turn on WhatsApp Fingerprint Lock for Android, you have to goto Settings > Account > Privacy > Fingerprint lock. Once you enable the Unlock with fingerprint option, you will have to confirm your phone fingerprint. This feature is currently rolling out global, all you need to do is to update yours to WhatsApp to version 2.19.308 from Google play store.