net: LookupHost shows different results between GODEBUG=netdns=cgo and go

What version of Go are you using (go version)?

go version go1.9.2 darwin/amd64

What did you do?

package main

import (
	"net"
	"fmt"
)

func main() {
	fmt.Println(net.LookupHost("10.256"))
	fmt.Println(net.LookupHost("10.256.1"))
	fmt.Println(net.LookupHost("10.10.256"))
	fmt.Println(net.LookupHost("10.10.256.1"))
	fmt.Println(net.LookupHost("10.10.10.256"))
}

What did you expect to see?

This program works fine on both Linux & Windows and does show below output, but not on Mac

[] lookup 10.256: no such host
[] lookup 10.256.1: no such host
[] lookup 10.10.256: no such host
[] lookup 10.10.256.1: no such host
[] lookup 10.10.10.256: no such host

What did you see instead?

[10.0.1.0] <nil>
[] lookup 10.256.1: no such host
[10.10.1.0] <nil>
[] lookup 10.10.256.1: no such host
[] lookup 10.10.10.256: no such host