UserAgent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Firefox/52.0

Steps to reproduce the problem:
1. Trying to use WebAssembly in chrome-extension
2. Can't fetch .wasm file
3. Can't access the module if loading the .js file

What is the expected behavior?

What went wrong?
fetch('simple.wasm').then(response =>
  response.arrayBuffer()
).then(bytes =>
  WebAssembly.instantiate(bytes, importObject)
).then(results => {
  results.instance.exports.exported_func();
});

producing the error:
      "Uncaught (in promise) TypeError: WebAssembly Instantiation: Import #0 module="env" error: module is not an object or function"
or
      "Uncaught (in promise) TypeError: Fail ed to fetch"

Accessing the .js file:
in background.html:
     <script src="index.js"></script>

and then just use the function exported:

     var result = _roll_dice();

BUT, in extension I only have a background.html file. So I'm looking for a way to access the Module which was loaded in the background file. and I need to call the function from a Worker.

I've tried:

chrome.extension.getBackgroundPage() can access the Module but can't send it to the Worker:

    Failed to execute 'postMessage' on 'Worker': # could not be cloned.

And if I try to stringify it first:

    Uncaught TypeError: Converting circular structure to JSON

(I tried to un-circular it, didn't work...)

And I can't call chrome.extension.getBackgroundPage() from the Worker because I can't access chrome API from there.

Did this work before? N/A 

Chrome version: <Copy from: 'about:version'>  Channel: n/a
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: Shockwave Flash 29.0 r0