This package provide customizable TCP net.Listener with various
performance-related options:
* SO_REUSEPORT. This option allows linear scaling server performance
on multi-CPU servers.
See https://www.nginx.com/blog/socket-sharding-nginx-release-1-9-1/ for details.
* TCP_DEFER_ACCEPT. This option expects the server reads from the accepted
connection before writing to them.
* TCP_FASTOPEN. See https://lwn.net/Articles/508865/ for details.
