add PROXY to apk package manager

.env.sample

@@ -1,3 +1,5 @@
 REGISTRY_URL=docker.registry
 IMAGE_NAME=packer-builder
 VERSION=1.0.0
+PROXY=
+

.gitignore

@@ -3,6 +3,7 @@
 *.iso
 *.tar
 *.bz2
+.env
 
 packer/assets/id_rsa_qemu*
 packer/assets/packer_cache/

docker-compose.yml

@@ -5,6 +5,8 @@ services:
       image: ${REGISTRY_URL}/${IMAGE_NAME}:${VERSION}
       build: 
          context: ./packer
+         args:
+           PROXY: "${PROXY}"
       entrypoint: "bash -c"
       command: "'while sleep 3600; do :; done'"
       stdin_open: true

packer/Dockerfile

@@ -1,5 +1,9 @@
 FROM hashicorp/packer:1.5.1
 
+ARG PROXY=""
+ENV http_proxy="${PROXY}"
+ENV https_proxy="${PROXY}"
+
 ARG USER=packer
 ARG GROUP=packer