Cdnjs.cloudflare.com returns a 404 error for 2.1.5

https://cdnjs.cloudflare.com/ajax/libs/gojs/2.1.5/go.js
https://cdnjs.cloudflare.com/ajax/libs/gojs/2.1.5/go-debug.js

Both return a 404 error.
2.0.5 works.

I don’t know why CDNJS is not up-to-date. Try unpkg instead:
https://unpkg.com/[email protected]/release/go.js

That works.
Thanks!