Thank you @cacholong,
I have successfully configured the plugin and now it works ??
Let me share my process if anyone is not familiar with how to pass parameter to php from nginx:
1. nano /etc/nginx/sites-available/{your_conf_file}
2. Find location ~ \.php$
block, and add fastcgi_param CC_NGINX_FASTCGI_CACHE_PATH /your/fastcgi/cache/path;
inside this block, remember to replace /your/fastcgi/cache/path
with your path.
3. Save and exit. run nginx -t
to test if the conf is correct.
4. service nginx reload
. Now navigate to your WordPress, the cache should be purgeable.
Cheers,
Atelier Shen