RouteServiceProvider.php

protected function mapAmpRoutes()
{
    Route::group([
        'middleware' => 'web',
        'namespace' => $this->namespace,
        'prefix' => 'amp',
    ], function ($router) {
        require base_path('routes/amp.php');
    });
}

public function map()
{
    // new amp routes
    $this->mapAmpRoutes(); 

    $this->mapWebRoutes();

    $this->mapApiRoutes();
}