How to override zf3 config based on router?

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I have this config:

'zf-mvc-auth' => [
    'authentication' => [
        'map' => [
            'ZF\\OAuth2' => 'session',
        ],
        'adapters' => [
            'session' => [
                'adapter' => 'Application\\Authentication\\Adapter\\SessionAdapter',
            ],
        ],
    ],
],

I need 2 APIs at the same site: one for admin and one for actually the site. It means I need 2 different session adapters for apigility. It looks like I can override config inside init(ModuleManager $moduleManager) method of Module.php but how to access to router in this method?

I need this checking:

if($matchedRouteName == 'admin' || strpos($matchedRouteName, 'admin/') === 0){

to set appropriate map key ‘ZF\OAuth2’. How to do that?