The new type [`KeepAliveConfig`](/pkg/net#KeepAliveConfig) permits fine-tuning
the keep-alive options for TCP connections, via a new
[`TCPConn.SetKeepAliveConfig`](/pkg/net#TCPConn.SetKeepAliveConfig) method and
new KeepAliveConfig fields for [`Dialer`](/pkg/net#Dialer) and [`ListenConfig`](/pkg/net#ListenConfig).