# File lib/rack/session/memcache.rb, line 61
      def set_session(env, session_id, new_session, options)
        expiry = options[:expire_after]
        expiry = expiry.nil? ? 0 : expiry + 1

        with_lock(env) do
          @pool.set session_id, new_session, expiry
          session_id
        end
      end