index.js

import { Comlink } from './node_modules/comlinkjs/comlink.es6.js';

const worker = new Worker('./node_modules/comlink-fetch/src/fetch.worker.js');

const proxy = Comlink.proxy(worker);

async function getSecondaryInfo() {
    const API = await new proxy.Fetch;

    API.setBaseUrl("https://jsonplaceholder.typicode.com/");
    API.setDefaultHeaders({ 'Content-Type': 'application/json' });
    API.setDefaultBody({ lang: 'en' });

    let page1 = API.get('posts/1');
    let page2 = API.get('posts/2');

    console.log(await page1);
    console.log(await page2);
}

getSecondaryInfo();