const golang.org/x/sys/unix.SO_KEEPALIVE

2 uses

	golang.org/x/sys/unix (current package)
		zerrors_linux_amd64.go#L354: 	SO_KEEPALIVE                     = 0x9

	google.golang.org/grpc/internal
		tcp_keepalive_unix.go#L50: 				unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_KEEPALIVE, 1)