How should I go about passing an `AsyncSocket` into another thread through a
channel? The sending-over-channel part seems to be working fine, but when I try
to `.send()` on the socket in the recipient thread, it tells me that the file
descriptor is not registered. I tried doing `inheritable = true` thinking that
had something to do with it, but I must be missing something still, because
nothing changed. Are file descriptors / socket handles tracked per-thread? If
so, how do I transfer them to another thread?