I remember in a github thread where Taylor said that people should be using middleware to handle things like this so create a middleware and then access the session data there.
If you really want to access session data inside your service providers, then you would have to move the web middlewares into the global middleware stack and then do it.
I've a variable ... that needs its content to be loaded from the session to share it with all views .. any Idea ?
Session are not available in the service providers as it gets started by a middleware.
However you can setup a view composer sending this session variable to the view. As the view composer callback is fired at the moment the view is rendered, session will be available.