func getNsRecords(domainName string) ([]string, error) {
	return dnsmsg.Lookup(domainName)
}
for getting NS records, try to get NS rr from DNS root servers.
package checker
import (
	"errors"
	"fmt"
	"net"
	"nschecker/dnsmsg"
	"nschecker/printer"
	"strings"
)
func in_array(str string, list []string) bool {
	for _, v := range list {
		v = strings.TrimSpace(v)
		if strings.ToLower(v) == strings.ToLower(str) {
			return true
		}
	}
	return false
}
func getExpectRecordValueList(expectString string) []string {
	list := strings.Split(expectString, ",")
	for i, v := range list {
		v = strings.TrimSpace(v)
		v = strings.TrimRight(v, ".")
		v = v + "."
		list[i] = v
	}
	return list
}