nginx反向代理cdn

https://wuyanteng.github.io/2017/09/17/%E4%BD%BF%E7%94%A8Nginx%E5%8F%8D%E5%90%91%E4%BB%A3%E7%90%86%E5%81%9Acache%E7%BC%93%E5%AD%98-%E5%AE%9E%E7%8E%B0CDN%E5%8A%9F%E8%83%BD/

http://blog.51cto.com/slaytanic/516093

https://win-man.com/faq/winmannew/2018/09/21/79355.html

https://www.osyunwei.com/archives/2084.html