Just to note that I'm having the same issue on a few dockers. At first I thought it was because I had an issue with my DNS (pihole) but changing unraid DNS to use 1.1.1.1 and 8.8.8.8 didn't fix.
To add assault to injury, when I try to add --format=docker as an extra parameter as suggested above, the docker don't compile anymore I receive the following error message:
-u 99:100
--format=docker 'coderaiser/cloudcmd'
unknown flag: --format
Any assistance will be appreciated!