If you are using CloudFlare or a similar CDN you will get an infinite loop error with the %{HTTPS} solutions provided here. If you're a CloudFlare user you'll need to use this:

AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;
use Illuminate\Support\Facades\Schema;
use Illuminate\Support\Facades\URL;
use Illuminate\Support\Facades\App;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        Schema::defaultStringLength(191);
        if (!request()->secure() && App::environment() === 'production') {
            URL::forceScheme('https');
            return redirect()->secure(request()->getRequestUri());
        }
    }

    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

Force http to https for CloudFlare DNS managment systems

# force https
RewriteEngine On
RewriteCond %{HTTP:X-Forwarded-Proto} =http
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

LaravelMiddlewareForForceHttps.php

<?php

namespace App\Http\Middleware;

use Closure;

use Illuminate\Support\Facades\App;
use Illuminate\Support\Facades\URL;

class HttpsProtocol
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        if (!$request->secure() && App::environment() === 'production') {
            URL::forceScheme('https');
            return redirect()->secure($request->getRequestUri());
        }
        return $next($request);
    }
}