evil.js

// Bad third-party code
var fs = require('fs');
require('fibers');

function fetchSomething() { // don't do this!
	var fiber = Fiber.current;
	fs.readFile(__filename, 'utf8', function(err, val) {
		fiber.run(val);
	});
	return Fiber.yield();
}

// Naive client code
console.log('I am innocent code!');
var data = fetchSomething();

output.txt

I am innocent code!

node.js:178
        throw e; // process.nextTick error, or 'error' event on first tick
        ^
Error: yield() called with no fiber running
    at fetchSomething (./evil.js:10:15)
    at Object.<anonymous> (./evil.js:15:12)
    at Module._compile (module.js:404:26)
    at Object..js (module.js:410:10)
    at Module.load (module.js:336:31)
    at Function._load (module.js:297:12)
    at Array.<anonymous> (module.js:423:10)
    at EventEmitter._tickCallback (node.js:170:26)