返回路径的上一级文件夹
Path.Combine(Path.Combine(Application.streamingAssetsPath, "../"), "cnm.txt")
返回路径的上两级文件夹
Path.Combine(Path.Combine(Application.streamingAssetsPath, "../../"), "cnm.txt")
返回路径的上三级文件夹
Path.Combine(Path.Combine(Application.streamingAssetsPath, "../../../"), "cnm.txt")