Core update by composer

Consider current site is in 8.3.5 version.

Below are the steps to update to latest 8.6.1 version.

Uninstall Drush

composer remove drush/drush

Uninstall Drupal Console and its dependencies

composer remove drupal/console drupal/console-core drupal/console-en drupal/console-extend-plugin

Update Drupal core

composer update drupal/core symfony/* --with-dependencies

Re-add Drush (older version ex. 8.1.16)

composer require drush/drush ~8.0 --update-with-dependencies

Update Drush (ex. 9.4.0)

composer update drush/drush --with-dependencies