Redis-based Session Option is not working

I wanted to use redis to save users' sessions. So i followed one sample,

<?php

namespace App\Extensions;

use Illuminate\Support\Facades\Redis as Redis;

class RedisSessionStore implements SessionHandlerInterface {

    public function open($savePath, $sessionName) {}

    public function close() {}

    public function read($sessionId) {
        $redis = Redis::connection('default');
        return $redis->get($sessionId);
    }

    public function write($sessionId, $data) {
        $redis = Redis::connection('default');
        $redis->set($sessionId, $data);
    }

    public function destroy($sessionId) {
        $redis = Redis::connection('default');
        $redis->command('del', $sessionId);
    }

    public function gc($lifetime) {
        //
    }
}

Above file is saved as RedisSessionStore.php and put in Extentions folder under app folder.

<?php

namespace App\Providers;

use Session;
use App\Extensions\RedisSessionStore;
use Illuminate\Support\ServiceProvider;

class SessionServiceProvider extends ServiceProvider {

    public function boot() {
        Session::extend('redis', function($app) {
            return new RedisSessionStore;
        });
    }

    public function register() {}
}

Above file is saved as SessionServiceProvider.php and put in Providers folder under app folder.

I have added App\Providers\SessionServiceProvider::class, into Providers in app/config/app.php file. And i have also changed the 'driver' => env('SESSION_DRIVER', 'file'), to 'driver' => env('SESSION_DRIVER', 'redis'),in app\config\session.php. But in fact it was still saving the session into file...Can anyone help me out?