Combine multifile yaml in Javascript

Question

I have my yaml files split up according to a structure like this:

.
├── index.yaml
├── info
│   └── index.yaml
├── definitions
│   └── index.yaml
│   └── User.yaml
└── paths
    ├── index.yaml
    ├── bar.yaml
    └── foo.yaml

index.yaml:

swagger: '2.0'
info:
  $ref: ./info/index.yaml
paths:
  $ref: ./paths/index.yaml
definitions:
  $ref: ./definitions/index.yaml

info/index.yaml:

version: 1.0.0
title: Service API

definitions/index.yaml

User:
  $ref: ./User.yaml

definitions/User.yaml

type: object
properties:
  name:
    type: string

...and so on (but you get the idea). I followed the guidance of a blog post that did exactly this. So before calling initializeMiddleware from the swagger-tools library, my understanding is that I need to merge all these yaml files into a single file. I tried doing that the way @mohsen____ describes in his blog, leveraging the json-refs library and calling the resolveRefs (or resolveRefsAt) function to get a promise-ified response object that contains a version of the document with the JSON references resolved. This doesn't seem to work though. When I try the following nothing gets logged to the console:

let options = {
    filter: ['relative', 'remote']
};

jsonRefs.resolveRefsAt('./swagger/index.yaml', options)
.then(function (res): any {
  console.dir(res);
  console.log(JSON.stringify(res.resolved, null, 2));
}, (err) => {
  console.error(err);
});