https://blog.wongcw.com/2020/07/01/opensignal%e7%99%bc%e5%b8%832020%e5%b9%b4%e4%b8%ad%e5%a0%b1%e5%91%8a%ef%bc%9a%e5%93%aa%e5%ae%b6%e7%be%8e%e5%9c%8b%e9%81%8b%e7%87%9f%e5%95%86%e7%9a%845g%e7%b6%b2%e9%80%9f%e6%9c%80%e5%bf%ab%ef%bc%9f/