Go check SSL/TLS

main.go

package main

import (
	"crypto/tls"
	"fmt"
	"time"
)

type target struct {
	domain string
	port   int
}

func (t *target) Url() string {
	if t.port == 0 {
		return fmt.Sprintf("%s:443", t.domain)
	}

	return fmt.Sprintf("%s:%d", t.domain, t.port)

}

func (t *target) CheckTLS() {
	conn, err := tls.Dial("tcp", t.Url(), nil)
	if err != nil {
		fmt.Println("[ERROR] Server doesn't support SSL certificate err: " + err.Error())
	} else {
		err = conn.VerifyHostname(t.domain)
		if err != nil {
			fmt.Println("Hostname doesn't match with certificate: " + err.Error())
		}

		expiry := conn.ConnectionState().PeerCertificates[0].NotAfter
		fmt.Printf("Issuer: %s\nExpiry: %v\n", conn.ConnectionState().PeerCertificates[0].Issuer, expiry.Format(time.RFC850))

		currentTime := time.Now()
		diff := currentTime.Sub(expiry)
		if diff > 0 {
			fmt.Println("EXPIRED!!")
		}

	}

}

func main() {

	urls := []target{
		{domain: "api-gad.io.italia.it"},
		{domain: "api.io.italia.it"},
		{domain: "app.io.italia.it"},
		{domain: "app-backend.io.italia.it"},
		{domain: "developerportal-backend.io.italia.it"},
		{domain: "developer.io.italia.it"},
		{domain: "io.italia.it"},
		{domain: "api.io.pagopa.it"},
		// {domain: "api-app.pagopa.it"},
		{domain: "api-mtls.io.pagopa.it"},
		{domain: "assets.cdn.io.italia.it"},
		{domain: "backoffice.io.italia.it"},
	}

	for _, u := range urls {
		fmt.Println(u.domain)
		u.CheckTLS()
		fmt.Println("")
	}

}