open only one file at a time
diff --git a/mc/mc.go b/mc/mc.go
index ab823d7..00169a3 100644
--- a/mc/mc.go
+++ b/mc/mc.go
@@ -42,6 +42,7 @@
 		for _, s := range args {
 			if f, err := os.Open(s); err == nil {
 				copyin(w, f)
+				f.Close()
 			} else {
 				log.Println(err)
 			}