HTTP Session give me NULL

SiteMiddleware.php

public function handle($request, Closure $next)
    {
        $siteDetails = siteData();

        // dd($siteDetails);

        if($siteDetails)
        {
            session(['siteData' => $siteDetails]);
            return $next($request);
        }
        else{
            dd("Hello");
        }
    }

helpers.php

function getTemplate()
{
    dd(session('siteData'));
}

function siteData()
{
    //using it in middleware for checking login

    $domain = $_SERVER['HTTP_HOST'];

    $siteDetails = \Illuminate\Support\Facades\DB::table('site_names as sn')
        ->join('sites as s', 's.id', '=', 'sn.site_id')
        ->join('users as u', 's.id', '=', 'u.site_id')
        ->leftJoin('css_templates as ct', 'ct.id', '=', 's.template_id')
        ->whereIn('u.user_type', [1, 2])
        ->where('sn.domain', $domain)
        ->select('u.site_id', 'u.id as site_admin', 'u.name', 's.*', 'ct.template_name', 'ct.css')
        ->first();

    dd($siteDetails);
}