When using Node.js cluster, how to pass ES client instance from master to worker?

When I use cluster module of Node.js to start multiple threads to do ES query, a problem occurs that the ES client instance can't be passed from master to workers.

In the function worker.send(message[, sendHandle][, callback]) of cluster module, message object will be serialized using JSON.stringify() internally. In this way, the ES client object will be destroyed when passing through message object.

Is there any way to share ES client instance between master and workers?

Thanks for your help.