Re: Upgrade / Migrate From Magento 2.1.9 to Magento 2.2.0 GA
Open your root composer.json file

Replace with below content,

«version»: «2.1.9» replace with «version»: «2.2.0»
«magento/product-community-edition»: «2.1.9» replace with «magento/product-community-edition»: «2.2.0»

run command from magento 2 root,

composer update
After successfully completed upgradation,

run

php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
if issue solved, Click kudos/Accept as solutions.

If Issue Solved, Click Kudos/Accept As solutions.