docker-compose build issue apk update failed

 https://stackoverflow.com/questions/53710206/docker-cant-build-because-of-alpine-error

It was a DNS error for me. By setting /etc/docker/daemon.json with,

{
  "dns": ["8.8.8.8"]
}

and then restarting docker with,

sudo service docker restart

NOTE: if you workaround network configs, this might break builds.