Getting Exception in gojs library while loading

I am using go 1.8 version and while loading gojs , I am getting the exception but strange thing is that it is happening sometimes, not everytime.

Thanks in advance

What is that token that the error message did not bother to say?
How is the go.js library being loaded?
Yes, it seems very odd that the browser cannot reliably load the same JS file multiple times. Do you have the same problem in other browsers?