fix "Can't set headers after they are sent to the client" error

src/downloader/got.ts

@@ -79,10 +79,14 @@ export class GotDownloader {
       .head(srv.url + url, this.getOptions(srv, 'head'))
       .then((r) => {
         res.set(r.headers);
-        res.sendStatus(r.statusCode);
+        if (!res.headersSent) {
+          res.sendStatus(r.statusCode);
+        }
       })
       .catch((r: { statusCode?: number }) => {
-        res.sendStatus(r?.statusCode ?? 404);
+        if (!res.headersSent) {
+          res.sendStatus(r?.statusCode ?? 404);
+        }
       });
   };
 

src/index.ts

@@ -57,10 +57,16 @@ const cacheRequestHandler: RequestHandler = (req, res, next) => {
           downloader.download(url, srv, res);
         }
       } else {
-        res.sendStatus(403);
+        if (!res.headersSent) {
+          res.sendStatus(403);
+        }
       }
     })
-    .catch(() => res.sendStatus(403));
+    .catch(() => {
+      if (!res.headersSent) {
+        res.sendStatus(403);
+      }
+    });
 };
 
 // init cache dir