reference: https://stackoverflow.com/questions/50177216/how-to-grant-all-privileges-to-root-user-in-mysql-8-0
Starting with MySQL 8 you no longer can (implicitly) create a user using the GRANT command. Use CREATE USER instead, followed by the GRANT statement:
CREATE USER 'root'@'%' IDENTIFIED BY 'root';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;
SELECT Host,User,authentication_string FROM mysql.user;