App doesn't exit if specify a worker

[tylerlong]

"elkjs": "^0.9.3",

Official sample code copied from readme page:

const ELK = require('elkjs')
const elk = new ELK()

const graph = {
  id: "root",
  layoutOptions: { 'elk.algorithm': 'layered' },
  children: [
    { id: "n1", width: 30, height: 30 },
    { id: "n2", width: 30, height: 30 },
    { id: "n3", width: 30, height: 30 }
  ],
  edges: [
    { id: "e1", sources: [ "n1" ], targets: [ "n2" ] },
    { id: "e2", sources: [ "n1" ], targets: [ "n3" ] }
  ]
}

elk.layout(graph)
   .then(console.log)
   .catch(console.error)

It works very well.

If I specify a worker url:

const ELK = require("elkjs");
const Worker = require("web-worker");

const workers = new Set();

const elk = new ELK({
  workerUrl: require.resolve("elkjs/lib/elk-worker.min.js"),
});

const graph = {
  id: "root",
  layoutOptions: { "elk.algorithm": "layered" },
  children: [
    { id: "n1", width: 30, height: 30 },
    { id: "n2", width: 30, height: 30 },
    { id: "n3", width: 30, height: 30 },
  ],
  edges: [
    { id: "e1", sources: ["n1"], targets: ["n2"] },
    { id: "e2", sources: ["n1"], targets: ["n3"] },
  ],
};

elk
  .layout(graph)
  .then((s) => {
    console.log(s);
    workers.forEach((worker) => worker.terminate());
  })
  .catch(console.error);

It works but it does NOT exit.

Which means the worker is still active.