diff --git a/eBook/12.5.md b/eBook/12.5.md
index 020cc6e..88b0a07 100644
--- a/eBook/12.5.md
+++ b/eBook/12.5.md
@@ -40,6 +40,7 @@ func main() {
 			continue
 		}
 		cat(bufio.NewReader(f))
+		f.Close()
 	}
 }
 ```