What a fiber-using function looks like if you let the fiber call `done` for you. Compare https://gist.github.com/wearhere/825a51a6a16a4337733f. More info at https://www.mixmax.com/blog/node-fibers-using-synchronize-js.

calling-done-automatically.js

function processFile(fileName, done) {
  sync.fiber(function() {
    // No need for try-catches even, assuming that you're ok with `done` handling errors!
    var data = /* first `sync` call */;
    return /* second `sync` call */;
  }, done);
}