clean up previously mounted folder

weed/mount/unmount/unmount_std.go

@@ -0,0 +1,18 @@
+//go:build !linux
+// +build !linux
+
+package unmount
+
+import (
+	"os"
+	"syscall"
+)
+
+func unmount(dir string) error {
+	err := syscall.Unmount(dir, 0)
+	if err != nil {
+		err = &os.PathError{Op: "unmount", Path: dir, Err: err}
+		return err
+	}
+	return nil
+}