code: func TrackWithTcpKeepAlive(keepalive time.Duration) listenerOpt {
  	return func(opts *listenerOpts) {
  		opts.tcpKeepAlive = keepalive
  	}
  }
docs: // TrackWithTcpKeepAlive makes sure that any `net.TCPConn` that get accepted have a keep-alive.
  // This is useful for HTTP servers in order for, for example laptops, to not use up resources on the
  // server while they don't utilise their connection.
  // A value of 0 disables it.