gistfile1.scala

          val newSession = additionalSessionParams.foldLeft[Session](request.session) { _ + _ }
          val r: PlainResult = action(request).asInstanceOf[PlainResult]
          // workaround since withSession calls aren't composable it seems
          val innerSession = r.header.headers.get(SET_COOKIE).map(cookies => Session.decodeFromCookie(Cookies.decode(cookies).find(_.name == Session.COOKIE_NAME)))
          if(innerSession.isDefined) {
            // there really should be an API method for adding sessions
            val combined = innerSession.get.data.foldLeft(newSession) { _ + _ }
            r.withSession(combined)
          } else {
            r.withSession(newSession)
          }