This is a very specialized Go library and, frankly, somewhat of a straw man: I've found myself needing to quickly assign ports on servers with a high density of highly ephemeral inbound/outbound connections where the protocol relies on a specific port number. Obviously, running sequentially through a list of ports until I find one I have not already allocated does not perform very well.

I was surprised when I did not find anything already addressing this need. So, this is the straw man part: surely I missed it!

Anyway, should you ever need something like that... here it is.