fix: close file on upload

main.go

@@ -52,6 +52,8 @@ func createUploadHandler(dir string) http.HandlerFunc {
 			httpFail(w, r, "Could not complete upload", err)
 			return
 		}
+		defer f.Close()
+
 		if _, err := io.Copy(f, r.Body); err != nil {
 			httpFail(w, r, "Could not complete upload", err)
 			return