validate path first before GET and HEAD

src/index.coffee

@@ -20,6 +20,9 @@ handleRequest = ({ request }) ->
 
 handleHEAD = (request) ->
   url = new URL request.url
+  if url.pathname.endsWith "/"
+    return new Response "Invalid URL",
+      status: 404
 
   resp = await s3.getObject url.pathname[1...], {}
 
@@ -30,6 +33,9 @@ handleHEAD = (request) ->
 
 handleGET = (request) ->
   url = new URL request.url
+  if url.pathname.endsWith "/"
+    return new Response "Invalid URL",
+      status: 404
 
   return await s3.getObject url.pathname[1...], {}