WireGuard object is not garbage collected

[thatsed]

Creating a WireGuard instance in a function will keep pipes open, thus preventing garbage collection and filling up file descriptors until they run out and the product throws OSError.

Workaround: declare a single WireGuard object per project, using a wrapper to implement it as singleton (either create a new object or return the same one if it has already been instantiated).

Proposed fix: make the WireGuard class a singleton, or make it so it will be garbage collected.

I can make a PR with the singleton implementation if you'd like.