add dns module

dns/dns.go

@@ -0,0 +1,36 @@
+package dns
+
+import (
+	"sync"
+
+	"github.com/babolivier/go-doh-client"
+)
+
+var resolver *doh.Resolver
+var once sync.Once
+
+func Init(dns string) {
+	getInstance().Host = dns
+}
+
+func LookupOverHttps(domain string) (string, error) {
+	a, _, err := resolver.LookupA(domain)
+	if err != nil {
+		return "", err
+	}
+
+	ip := a[0].IP4
+
+	return ip, nil
+}
+
+func getInstance() *doh.Resolver {
+	once.Do(func() {
+		resolver = &doh.Resolver{
+			Host:  "",
+			Class: doh.IN,
+		}
+	})
+
+	return resolver
+}