try to fix hashing

src/util.ts

@@ -1,10 +1,8 @@
 import { createHash } from "node:crypto";
 
-const hasher = createHash("sha256");
-
 export const hashDigest = (payload: string | Buffer) =>
     "sha-256="
-    + hasher
+    + createHash("sha256")
         .update((Buffer.isBuffer(payload) ? payload : Buffer.from(payload)).toString("hex"))
         .digest("base64");