Revert "use golang:1.12 instead of cicleci/golang:1.12"
Revert "use golang:1.12 instead of cicleci/golang:1.12"

This reverts commit 6381f31113c59f4c73336a74f6078adacbd9cef6.

grubernaut/packer,dave2/packer,rnaveiras/packer,dave2/packer,dave2/packer,dave2/packer,hashicorp/packer,tas50/packer,paulmey/packer,ricardclau/packer,ricardclau/packer,rnaveiras/packer,dave2/packer,grubernaut/packer,timsutton/packer,rnaveiras/packer,mitchellh/packer,ricardclau/packer,dave2/packer,bryson/packer,ricardclau/packer,paulmey/packer,hashicorp/packer,ricardclau/packer,tas50/packer,rnaveiras/packer,paulmey/packer,paulmey/packer,pecigonzalo/packer,pecigonzalo/packer,tas50/packer,bryson/packer,mitchellh/packer,pecigonzalo/packer,timsutton/packer,tas50/packer,timsutton/packer,mitchellh/packer,timsutton/packer,rnaveiras/packer,timsutton/packer,bryson/packer,mitchellh/packer,paulmey/packer,hashicorp/packer,mitchellh/packer,timsutton/packer,ricardclau/packer,tas50/packer,grubernaut/packer,grubernaut/packer,rnaveiras/packer,grubernaut/packer,bryson/packer,grubernaut/packer,paulmey/packer,pecigonzalo/packer,hashicorp/packer,tas50/packer,bryson/packer,bryson/packer