refactor: migrate dlcache to struct

internal/dlcache/utils.go

@@ -0,0 +1,16 @@
+package dlcache
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"io"
+)
+
+func hashID(id string) (string, error) {
+	h := sha1.New()
+	_, err := io.WriteString(h, id)
+	if err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(h.Sum(nil)), nil
+}