Enhance DNS and Dialer (#341)

transport/internet/system_dialer_context.go

@@ -0,0 +1,18 @@
+package internet
+
+import "context"
+
+type systemDialer int
+
+const systemDialerKey systemDialer = 0
+
+func ContextWithLookupDomain(ctx context.Context, domain string) context.Context {
+	return context.WithValue(ctx, systemDialerKey, domain)
+}
+
+func LookupDomainFromContext(ctx context.Context) string {
+	if domain, ok := ctx.Value(systemDialerKey).(string); ok {
+		return domain
+	}
+	return ""
+}