authentication plugin 'caching_sha2_password' cannot be loaded code example

Example 1: MySQL said: Authentication plugin 'caching_sha2_password' cannot be loaded: dlopen(/usr/local/lib/plugin/caching_sha2_password.so, 2): image not found

ALTER USER 'username'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';

restert mysql 
sudo mysql.server restart

Example 2: Unable to load authentication plugin 'caching_sha2_password'

ALTER USER 'student'@'localhost' IDENTIFIED WITH mysql_native_password BY 'pass123';