symfony 4.2 load doctrine service in connection wrapper class - symfony

Question

iam new to symfony and created some project based on 4.2 as i have to dynamically switch the db and there seems to be a bug in this version, i followed some instruction to setup a wrapper class for connecting to the db, this works fine. But iam struggeling with getting the doctrince method getConnections() here to work, to be able to double check the sended parameter against my db config. Everything i tried by initializing the doctrine as service container etc. doesn't work.
Hope someone could give me a hint, also my first post, so please no hate (:
Greetings
doctrine:
dbal:
default_connection: db_name
connections:
my_connection:
wrapper_class: App\Doctrine\DynamicConnection
url: '%env(DATABASE_URL)%'
driver: 'pdo_mysql'
server_version: '5.7'
charset: utf8mb4
services:
# default configuration for services in *this* file
_defaults:
public: false
autowire: true # Automatically injects dependencies in your services.
autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.
App\Doctrine\:
resource: '../src/Doctrine'
tags: ['doctrine.service_arguments']
doctrine.entity_manager:
public: true
class: App\Doctrine\DynamicConnection
arguments: [ '#doctrine.orm.entity_manager' ]
namespace App\Doctrine;
use Doctrine\DBAL\Connection;
use Doctrine\DBAL\Driver;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\DependencyInjection\ContainerBuilder;
class DynamicConnection extends Connection
{
public function __construct(array $params = array(), Driver $driver = null, $config = null, $eventManager = null)
{
#$request = Request::createFromGlobals();
#$dbname = $request->query->get('db_name');
$containerBuilder = new ContainerBuilder();
var_dump($containerBuilder->getServiceIds());
$doctrine = $containerBuilder->get('doctrine.entity_manager');