add domain whois/dns support, refactor codebase

internal/db/utils.go

@@ -0,0 +1,27 @@
+package db
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io"
+	"os"
+)
+
+// fileMD5 calculates the MD5 hash of a file.
+func fileMD5(path string) (string, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer func() {
+		if err := file.Close(); err != nil {
+			fmt.Printf("Error closing file: %v\n", err)
+		}
+	}()
+
+	hash := md5.New()
+	if _, err := io.Copy(hash, file); err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%x", hash.Sum(nil)), nil
+}