error calling index: index out of range: 1, but "last works

[maxmeyer]

I get this error when I use the index-method with docker-gen on something else than 0, but the last and first-methods work as expected. I can't really see what I do wrong.

2018/03/08 23:22:34 Template error: template: vhost-nginx-new.tmpl:10:3: executing "vhost-nginx-neu.tmpl" at <index $v 1>: error calling index: index out of range: 1

This is an "annotated" template showing the results for the example given below:

{{ range $value := whereExist . "Env.VIRTUAL_HOST" }}
{{ range $index, $vhost := split $value.Env.VIRTUAL_HOST "," }}
{{ $v := split $vhost ":::" }}
# this is the content of $v after splitting up the string
# [nextcloud-1.cloud.in.example.org nextcloud-1:80]
{{ $v }}

{{ $frontend := first $v }}
# this succeeds with:
# nextcloud-1.cloud.in.example.org
{{ $frontend }}

{{ $backend := last $v }}
# this succeeds with
# nextcloud-1:80
{{ $backend }}


{{ index $v 0 }}
# this succeeds with
# nextcloud-1.cloud.in.example.org

{{ index $v 1 }}
# this fails with
# error calling index: index out of range: 1
{{ end }}
{{ end }}

The docker container is started this way:

/usr/bin/docker run \
  --rm \
  --name nextcloud-1 \
  --network internal \
  -v /srv/machines/nextcloud/storage:/var/www/html \
  -e VIRTUAL_HOST=nextcloud-1.cloud.in.example.org:::nextcloud-1:80 \
  nextcloud:13

That's the template for docker-gen:

{{ range $value := whereExist . "Env.VIRTUAL_HOST" }}
{{ range $index, $vhost := split $value.Env.VIRTUAL_HOST "," }}
{{ $v := split $vhost ":::" }}
{{ $v }}
{{ $frontend := first $v }}
{{ $frontend }}
{{ $backend := last $v }}
{{ $backend }}
{{ index $v 0 }}
{{ index $v 1 }}
{{ end }}
{{ end }}

That's the docker-gen-configuration-file

[[config]]
template = "/etc/docker-gen/templates/vhost-nginx-new.tmpl"
dest = "/var/docker-gen/exports/nginx/vhosts-new.conf"
watch = true
keep-blank-lines = true
notify-output = true

[maxmeyer]

@jwilder Any ideas?