Session issue in Laravel 5.1

My app is built with Laravel 5.1. I have saved some data in session using the code, session(['first_name' => Auth::user()->first_name]). The value is set when user is logging in. It's working most of the times but sometimes the session value is being null. I don't know why automatically the session value is getting null. I am tired of solving this kind of weird problem. I need help.

via Chebli Mohamed