stack trace for unhandled promise rejection

script.js

 #!/usr/bin/env node
 
+process.on("unhandledRejection", err => {
+	console.error("Unhandled rejection");
+	console.trace(err);
+	process.exit(1);
+});
+
 var dns = require("dns");
 var StratumClient = require("./js/stratum-client");
 var CPUMiner = require("./js/miner-cpu");