fixed serving of directory named 'index.html'

main.go

@@ -173,8 +173,8 @@ func main() {
 		}
 
 		// serve index.html if present (case-sensitive)
-		indexPath := filepath.Join(fpath, "index.html")
-		if _, err := os.Stat(indexPath); err == nil {
+		indexPath := fpath + "/index.html"
+		if indexInfo, err := os.Stat(indexPath); err == nil && !indexInfo.IsDir() {
 		    http.ServeFile(w, r, indexPath)
 			return
 		}