I am developing server that utilize Apple Push Notification Service with Go language. After deploy on Rackspace cloud server it stopped to work telling certificate signed by unknown authority

openssl verify cert.pem

tells

error 20 at 0 depth lookup:unable to get local issuer certificate

Fix is to append missing certificate to /etc/ssl/certs/ca-certificates.crt

https://www.entrust.net/downloads/binary/entrust_2048_ca.cer

Backup /etc/ssl/certs/ca-certificates.crt first

wget https://www.entrust.net/downloads/binary/entrust_2048_ca.cer

cat entrust_2048_ca.cer >> /etc/ssl/certs/ca-certificates.crt first