Calculate if certificate expiry is within duration

func main() {
	pk, err := os.ReadFile("./domain.crt")
	if err != nil {
		log.Fatal("error reading file: ", err)
	}

	pp, _ := pem.Decode(pk)
	if pp == nil {
		log.Fatal("unable to decode public key")
	}

	cert, err := x509.ParseCertificate(pp.Bytes)
	if err != nil {
		log.Fatal("unable to parse certificate: ", err)
	}

	{
		fmt.Println()
		fmt.Println("Duration: 3 Hours")
		fmt.Println("==================")
		fmt.Printf("Current date/time:        %s\n", time.Now().Format(time.RFC3339))
		fmt.Printf("Certificate Expiration:   %s\n", cert.NotAfter.Format(time.RFC3339))

		d, err := time.ParseDuration("3h")
		if err != nil {
			log.Fatal("unable to parse duration: ", err)
		}

		if time.Now().Add(d).Before(cert.NotAfter) {
			fmt.Printf("Status:                   %s\n", "Certificate not ready for rotation")
		} else {
			fmt.Printf("Status:                   %s\n", "Certificate is ready for rotation")
		}
	}

	{
		fmt.Println()
		fmt.Println("Duration: 125 Hours")
		fmt.Println("==================")
		fmt.Printf("Current date/time:        %s\n", time.Now().Format(time.RFC3339))
		fmt.Printf("Certificate Expiration:   %s\n", cert.NotAfter.Format(time.RFC3339))

		d, err := time.ParseDuration("120h")
		if err != nil {
			log.Fatal("unable to parse duration: ", err)
		}

		if time.Now().Add(d).Before(cert.NotAfter) {
			fmt.Printf("Status:                   %s\n", "Certificate not ready for rotation")
		} else {
			fmt.Printf("Status:                   %s\n", "Certificate is ready for rotation")
		}
	}
}