Posted by vickey on October 15, 2018 at 6:30am
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
# [drush updb - won't work in the latest drush version due to issue - https://github.com/drush-ops/drush/issues/2152]
#### Re-add Drupal Console and its dependencies
composer require webflo/drupal-finder symfony/debug:~3.0 drupal/console-core drupal/console drupal/console-en