一般证书上，对CRT和PEM证书没有特别做区分，故在nginx上部署了xxx.com_public.crt证书，发现curl 接口，出现如下错误：
curl 'https://xxx.com/api/campaign-names'
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.se/docs/sslcerts.html
curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
需要加上 -k 才能正确访问；若直接使用pem证书，则无需加上 -k 参数；
Continue reading 关于nginx证书的问题.
