func (f *FileSystemDriver) keyPath(key string) string {
fileKey := hashutil.Md5(key)
return filepath.Join(f.Root, fileKey[:2], fileKey[2:4], fileKey[4:])
}
func (m *SimpleMediator) Key(ctx *app.Context) string {
return hashutil.Md5(ctx.R.Method + ctx.R.URL.String())
}