laravel-sample/app/Http/Middleware/ForceHttps.php

<?php
// app/Http/Middleware/ForceHttps.php
namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;

class ForceHttps
{
    public function handle(Request $request, Closure $next)
    {
        if (!$request->secure()) {
            return redirect()->secure($request->getRequestUri());
        }

        return $next($request);
    }
}