Variables not available in after_script

Summary

environment variable not available in after_script

Steps to reproduce

test:
  stage: test
  before_script:
    - export VERSION=$(if [ -n "${FILEVERSION}" ] && [ -f "${FILEVERSION}" ] ; then echo $(cat $FILEVERSION); else echo ${CI_BUILD_REF_NAME}; fi )
  script:
    - echo "version : ${VERSION}"
  after_script:
    - echo "version : ${VERSION}"

Actual behavior

result :

$ echo $VERSION
version : 1.0.1
Running after script...
$ echo $VERSION
version : 

Expected behavior

result expected :

$ echo $VERSION
version : 1.0.1
Running after script...
$ echo $VERSION
version : 1.0.1

Environment description

In kubernetes cluster Gitlab runner info : Docker

$ docker info
Containers: 98
 Running: 69
 Paused: 0
 Stopped: 29
Images: 41
Server Version: 1.13.1
Storage Driver: overlay
 Backing Filesystem: extfs
 Supports d_type: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
 Log: 
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: aa8187dbd3b7ad67d8e5e3a15115d3eef43a7ed1
runc version: 9df8b306d01f59d3a8029be411de015b7304dd8f
init version: 949e6fa
Kernel Version: 4.4.102-k8s
Operating System: Debian GNU/Linux 8 (jessie)
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 15.67GiB
Name: ip-172-20-36-91
ID: B7DL:PVDV:2QIH:O5BY:N54Q:55ZZ:MGRZ:VVE7:FZ3C:EXJZ:5RTD:IUF7
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false

Used GitLab Runner version

gitlab-runner --version
Version:      10.1.0
Git revision: c1ecf97f
Git branch:   10-1-stable
GO version:   go1.8.3
Built:        Sat, 21 Oct 2017 21:33:42 +0000
OS/Arch:      linux/amd64