报错如下：

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IDENTIFIED BY 'root' WITH GRANT OPTION' at line 1.

解决办法：

mysql> CREATE USER 'root'@'%' IDENTIFIED BY 'PASSWORD';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;
mysql> FLUSH PRIVILEGES;

参考文章：
How to grant all privileges to root user in MySQL 8.0

MySql 创建用户后无法连接解决方案
解决连接不上远程mysql数据库问题