An exception occurred in driver: SQLSTATE[HY000] [1045] Access denied for user 'db_user'@'localhost' (using password: YES)

I followed this documentationto add doctrine to my symfony project(v4.2). But when doctrine is installed it deosn't add this line to my project ( in my .env file like mentioned in the doc ):

DATABASE_URL="mysql://db_user:db_password@127.0.0.1:3306/db_name"

So I added it manually like this :

DATABASE_URL="mysql://root@127.0.0.1:3306/db_school"

and used this commande to create the database :

php bin/console doctrine:database:create

and it gives me this error :

In AbstractMySQLDriver.php line 93: An exception occurred in driver: SQLSTATE[HY000] [1045] Access denied for user 'db_user'@'localhost' (using password: YES)

In PDOConnection.php line 31: SQLSTATE[HY000] [1045] Access denied for user 'db_user'@'localhost' (using password: YES)
In PDOConnection.php line 27: SQLSTATE[HY000] [1045] Access denied for user 'db_user'@'localhost' (using password: YES)

Even I changed the user and password it still dosn't recognize it . Any idea why it dosn't work ? I will appreciate it .