Wordpress and MySQL: Error establishing a database connection

Hi, I am trying to launch a demo application with Kubernetes, and I follow this Example: Deploying WordPress and MySQL with Persistent Volumes - Kubernetes

I used kubeadm, create a cluster with 1 master and 1 worker. I changed the service type to NodePort, create PV. Everything is running now but I can not access the service because " Error establishing a database connection"

This is my YML files:

Thanks for your supporting