Firefox: `CloseNow` returns "A parameter or an operation is not supported by the underlying object"

Hi there, I noticed in Firefox WASM calling `CloseNow` returns an error:

> A parameter or an operation is not supported by the underlying object

This can be fixed by instead calling `Close(websocket.StatusNormalClosure, "some reason")`.

Since `CloseNow` is just an alias for `Close(websocket.StatusGoingAway, "")` my guess is that the empty reason value is being rejected by the browser,