Rack session

app.rb

session[:key] = 'value'
request.session['key']

config.ru

# Start Rack-server

use Rack::Session::Cookie, key: 'rack.session',
                           domain: '0.0.0.0',
                           path: '/',
                           expire_after: 2_592_000,
                           secret: Random.new.bytes(32)

run App