Gotify notification when certificate expire

check_certificate.sh

#!/bin/bash

certificat=/usr/certificate/example.com/cert.pem
gotify_url="https://push.example.com/message?token=xxxxx"
gotify_title="Synology Certificate Expiry"

function check_certificat () {
	if openssl x509 -checkend $((${1}*86400)) -noout -in $certificat; then
		return 1
	else
		return 0
	fi
}

function notification () {
	curl $gotify_url -F "title=${gotify_title}" -F "message=${1}"
}

# Certificate already expired
if check_certificat 0; then
	notification "Certificate expired"
# 1 day remaining
elif check_certificat 1; then
	notification "Less than 24 hours remaining before expiration of the certificate"
# 2 days remaining
elif check_certificat 2; then
	notification "2 days remaining before expiration of the certificate"
# 5 days remaining
elif check_certificat 5; then
	notification "5 days remaining before expiration of the certificate"
# 10 days remaining
elif check_certificat 10; then
	notification "10 days remaining before expiration of the certificate"
fi