nsqlookup/topology.go
func ClientIP(ctx context.Context) net.IP {
	ip, _ := ctx.Value(clientIPKey{}).(net.IP)
	return ip
}
func ClientIP(ctx context.Context) net.IP {
	ip, _ := ctx.Value(clientIPKey{}).(net.IP)
	return ip
}
// ClientIP returns the client IP embedded in the context, or nil if none were
// found.