upd

internal/domain/domain.go

@@ -0,0 +1,16 @@
+package domain
+
+import "strings"
+
+func HostWithoutPort(host string) string {
+	host = strings.TrimSpace(strings.ToLower(host))
+	if i := strings.IndexByte(host, ':'); i >= 0 {
+		return host[:i]
+	}
+	return host
+}
+
+func IsMckoDomain(host string) bool {
+	host = HostWithoutPort(host)
+	return strings.Contains(host, ".mcko.") || strings.HasPrefix(host, "mcko.")
+}