How do I use only fingerprint to unlock my phone? I got a Moto G4 Plus recently. It has a pretty fast fingerprint sensor. For my own reasons I don't want a secondary/backup(pattern/pin/etc) method to unlock my phone. I want to unlock it solely using my fingerprint. I'm ready to root it if needed. I know this comes with risks of being locked out of my phone or other emergencies, I'm ready for it. Does anyone have a way of achieving this?
That isn't possible.

Android encrypts a lot of your data when the phone turns off so no one can access your files. The key to that encryption, however, is the hard password you don't want to use. A fingerprint cannot be used a an encryption key because it is a system that has an error tolerance, and therefore does not work as an encryption key. 

In other words, this is impossible under any circumstance. It's just how Android works.