func Fqdn(domain string) string {
	if len(domain) > 0 && strings.HasSuffix(domain, ".") {
		return domain
	}
	return domain + "."
}
Fqdn normalize domain make sure it ends with '.'
package dns
import (
	"encoding/binary"
	"strings"
	"time"
	"golang.org/x/net/dns/dnsmessage"
	"github.com/v2fly/v2ray-core/v4/common"
	"github.com/v2fly/v2ray-core/v4/common/errors"
	"github.com/v2fly/v2ray-core/v4/common/net"
	dns_feature "github.com/v2fly/v2ray-core/v4/features/dns"
)