expires-session-without-a-domain.rb

class MigrateCookie < Struct.new(:app)
  def call env
    cookies = Rack::Utils.parse_query(env['HTTP_COOKIE'], ';,')
    case cookies['_session_id']
    when Array
      status, headers, body = app.call(env)
      headers['Set-Cookie'] =
        "#{headers['Set-Cookie']}\n#{expire_old_session}"
      [status, headers, body]
    else
      app.call(env)
    end
  end

  private
  def expire_old_session
    "_session_id=deleted; path=/;" \
    " expires=Thu, Jan 01 1970 00:00:00 UTC; HttpOnly"
  end
end