Using rack cas with sinatra and rack

Sinatra needs to set Rack::Session::Cookie before Rack::CAS:

# config.ru
require 'rack/cas'
use Rack::Session::Cookie, secret: 'verystrongsecret'
use Rack::CAS, server_url: 'https://cas.example.com'
require './my_app'
run MyApp

For more Options on Rack::Session::Cookie see Rack::Session::Cookie

# my_app
require 'sinatra'
class MyApp < Sinatra::Base
  before do
    halt 401 unless request.session['cas'] and request.session['cas']['user']
  end

  get "/" do
    request.session['cas'].inspect
  end
end