Update Drupal core via Drush

- Activate maintenance mode

drush state-set system.maintenance_mode 1

- Clear the cache

drush cache-rebuild

- Update the Files : please choose one of the below options

    - Update Drupal 8 core
           drush pm-update drupal

    - Update a single module
          drush pm-update module_name

    - Update only security updates
         drush pm-update --security-only