synchronous Read using nsIChannel

syncRead.js

const { Cu, Ci } = require('chrome');
const { NetUtil } = Cu.import('resource://gre/modules/NetUtil.jsm');

let charset = 'UTF-8';

let channel = NetUtil.newChannel('chrome://foo/content/test-file.txt', charset, null);
// `channel` obtained is an nsIChannel object. Open the channel synchronously.
let stream = channel.open(); 

// Get the stream length
let count = stream.available();
// Read the input stream and convert to string.
let data = NetUtil.readInputStreamToString(stream, count, { charset: charset });
// Close the input stream
stream.close();

console.log(data);