This method is bugging me for various reasons. For one, it reminds me why I wasn't sure about including the canvas API in js/dom: The same getContext function is used to get a WebGL context, which we almost definitely don't want to support. And the way the function is currently written, it only implements half of getContext and can't possibly support the other half. On top of that, now the `param` argument is almost pointless.

What I would suggest is having two methods: `GetContext2d() *CanvasRenderingContext2D` and `GetContext(param string) js.Object` – That way we 

1. do not have an unnecessary argument for the common case
2. can provide a working GetContext which simply returns the raw `js.Object`, so that other packages can use it.