opaque object inside a Cron timer is assumed to be a string which causes unmarshal errors

function OnUpdate(doc,meta) {

    var expiry = Math.round((new Date()).getTime() / 1000) + 30;

    var time_rand = random_gen(); // ----> int

    log('creating crontimer : ', time_rand);

    cronTimer(NDtimerCallback, time_rand, expiry);

}

function NDtimerCallback(docid, expiry) {

    log('creating bucket op : ', docid);

    dst_bucket[docid] = 'from NDtimerCallback';

}

function random_gen(){

    var rand = Math.floor(Math.random() * 20000000) * Math.floor(Math.random() * 20000000);

    var time_rand = Math.round((new Date()).getTime() / 1000) + rand;

    return time_rand;

}

2018-03-14T00:07:44.095-07:00 [Error] Consumer::getCronTimerCallback [worker_cron_timer_op_retry_1:/tmp/127.0.0.1:8091_worker_cron_timer_op_retry_1.sock:27944] Bucket fetch failed for cron timer key: <ud>cron_timer_op_retry::2018-03-14T07:07:24Z0</ud> val: <ud>&{[{NDtimerCallback }] }</ud>, err: json: cannot unmarshal number into Go value of type string

{

  "cron_timers": [{

    "callback_func": "NDtimerCallback",

    "payload": 274700495669869

  }, {

    "callback_func": "NDtimerCallback",

    "payload": 185158701515478

  }, {

    "callback_func": "NDtimerCallback",

    "payload": 10458915851862

  }],

  "counter": 3,

  "version": "vulcan"

}