实现该功能，不用借助第三方库，用go的标准库就足够了…
以下程序可以获取这些域名的SSL证书的到期时间，并在证书距离现在不足7天过期时打印提示：
package mainimport ("crypto/tls""fmt""net""time"
)func main() {domains := []string{"google.com","github.com","stackoverflow.com","amazon.com","microsoft.com","apple.com","netflix.com","facebook.com","twitter.com","linkedin.com",}for _, domain := range domains {expirationDate, err := getCertificateExpirationDate(domain)if err != nil {fmt.Printf("Error getting certificate for %s: %v\n", domain, err)continue}daysUntilExpiration := int(expirationDate.Sub(time.Now()).Hours() / 24)if daysUntilExpiration <= 7 {fmt.Printf("WARNING: Certificate for %s will expire in %d days (on %s)\n", domain, daysUntilExpiration, expirationDate.Format("2006-01-02"))} else {fmt.Printf("Certificate for %s will expire in %d days (on %s)\n", domain, daysUntilExpiration, expirationDate.Format("2006-01-02"))}}
}func getCertificateExpirationDate(domain string) (time.Time, error) {conn, err := tls.Dial("tcp", domain+":443", &tls.Config{InsecureSkipVerify: true,})if err != nil {return time.Time{}, err}defer conn.Close()cert := conn.ConnectionState().PeerCertificates[0]return cert.NotAfter, nil
}
执行代码,输出:
Certificate for google.com will expire in 61 days (on 2024-08-26)
Certificate for github.com will expire in 255 days (on 2025-03-07)
Certificate for stackoverflow.com will expire in 45 days (on 2024-08-09)
Certificate for amazon.com will expire in 196 days (on 2025-01-07)
Certificate for microsoft.com will expire in 354 days (on 2025-06-14)
Certificate for apple.com will expire in 63 days (on 2024-08-27)
Certificate for netflix.com will expire in 121 days (on 2024-10-24)
WARNING: Certificate for facebook.com will expire in 7 days (on 2024-07-02)
Certificate for twitter.com will expire in 157 days (on 2024-11-29)
Certificate for linkedin.com will expire in 35 days (on 2024-07-30)
对于A记录,其实都好说~
但是对于CNAME, 其实是有两套证书----CNAME并不是301,访问 https://baidu.mydomain.com 时并不是跳转到 https://baidu.com/，而是https://baidu.mydomain.com的内容,和https://baidu.com/完全一样
所以对于此处, 如果我是mydomain.com的持有者和维护者, 我只需要关心 baidu.mydomain.com 的证书到期时间,而不用管baidu.com的证书到期时间 (虽然事实上,baidu
.mydomain.com的证书,也可以被baidu.com的维护者一起帮忙维护，但一般是mydomain.com的持有者自己维护)
所以,检测CNAME记录时，应该关心"baidu.mydomain.com"的证书到期时间,不用管"baidu.com"—这个是baidu那边的事情
