Hotswap documentation example code has a race condition

[arosien]

The Hotswap documentation has an example where a Hotswap is used to manage a rotating file handle, but introduces a race condition attempting to store the current file into a Ref after the swap occurs. If a different fiber tries to write a log line, the Ref is read, but it could have been released from a swap call before the Ref.set call happens.

Instead the example should only use Hotswap.get to act on the current file handle.

[arosien]

thanks @armanbilge !