# docker exec -it db_mysql sh
# mysql --version
mysql Ver 8.0.11 for Linux on x86_64 (MySQL Community Server - GPL)
# mysql -uroot -proot
mysql> ALTER USER 'root'@'%' IDENTIFIED BY 'root' PASSWORD EXPIRE NEVER;
mysql> ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY 'root';
mysql> ALTER USER 'root'@'%' identified by 'your_passwd';
mysql> FLUSH PRIVILEGES;
mysql> exit;