macOS 状态栏显示实时网速的小工具, macOS menubar app to minitor internet speed.
使用 macOS 中的 nettop 命令，即可查看当前时刻各进程已经 download 和 upload 的字节数，持续按时执行 nettop 命令然后求差，即可得知网速详情。
Use the nettop command of macOS, we can get the uploaded and downloaded bytes of each process. By continuously execute the nettop command, we can know the net speed of each process.