curl命令忽略ssl证书进行https请求

某些情况下，服务器证书过期，或者证书不被识别：

SSL certificate problem: certificate has expired

SSL证书忽略校验，使用

-k

注意是小写的k，意思是：允许curl使用非安全的ssl连接并且传输数据（证书不受信）。

curl -v -k https://xxx.xxxx.xxx/xx

整个SSL的握手过程终于正常进行了：

* SSLv3, TLS handshake, Client hello (1):
* SSLv3, TLS handshake, Server hello (2):
* SSLv3, TLS handshake, CERT (11):
* SSLv3, TLS handshake, Server finished (14):
* SSLv3, TLS handshake, Client key exchange (16):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):
* SSLv3, TLS change cipher, Client hello (1):
* SSLv3, TLS handshake, Finished (20):