Remove unused mutex
diff --git a/memmap.go b/memmap.go
index 0b4edf4..e8e7824 100644
--- a/memmap.go
+++ b/memmap.go
@@ -26,8 +26,6 @@
 	"github.com/spf13/afero/mem"
 )
 
-var mux = &sync.Mutex{}
-
 type MemMapFs struct {
 	sync.RWMutex
 	data map[string]File