test: the worker thread in fact has no chance of receiving messages from the main thread

[jacobbubu]

https://github.com/Venemo/node-lmdb/blob/master/test/threads.js#L86
I'm trying to add console.log as following:

at line 86

...
process.on('message', function(msg) {
    console.log('worker received', msg) // no any output here
    if (msg.key) {
      var txn = env.beginTxn({readOnly: true});
    ...