Docker image prints out errors when setting TIMEZONE

[snowl]

I have these issues when I use the adferrand/dnsrobocert:latest docker image with the TIMEZONE variable set:

Waiting for DNS
/run.sh: 6: ping: not found
/run.sh: 6: ping: not found
/run.sh: 7: apk: not found
Setting timezone to Australia/Melbourne
/run.sh: 16: apk: not found