Concatenate variable in string

Question

How can I concatenate a variable in a string that is used a Go template? This is the original line (from https://github.com/nginx-proxy/nginx-proxy/blob/master/nginx.tmpl):

{{ $host := trim $host }}
{{ $is_regexp := hasPrefix "~" $host }}
{{ $upstream_name := when $is_regexp (sha1 $host) $host }}

{{ $access_log := (or (and (not $.Env.DISABLE_ACCESS_LOGS) "access_log /var/log/nginx/access.log vhost;") "") }}

I am trying to use variable "host" in that string like this:

{{ $host := trim $host }}
{{ $is_regexp := hasPrefix "~" $host }}
{{ $upstream_name := when $is_regexp (sha1 $host) $host }}

{{ $access_log := (or (and (not $.Env.DISABLE_ACCESS_LOGS) "access_log /var/log/nginx/" + $host + "_access.log vhost;") "") }}

But I get this error:

Unable to parse template: template: nginx.tmpl:175: illegal number syntax: "+"

Does this answer your question? [Is there an efficient way to concatenate strings](https://stackoverflow.com/questions/45389802/is-there-an-efficient-way-to-concatenate-strings) — Jonathan Hall, Jan 27 '21 at 20:13
Unfortunately no , I can't create a function inside a template: Unable to parse template: template: nginx.tmpl:175: function "func" not defined — brgsousa, Jan 27 '21 at 21:29
I am thinking I will have to edit this https://github.com/jwilder/docker-gen/blob/master/template.go and recompile this project so I can use the function strings.Join() — brgsousa, Jan 27 '21 at 21:43
`strings.Join` isn't the only option provided in the duplicate. — Jonathan Hall, Jan 28 '21 at 08:21

score 0 · Answer 1 · answered Jan 28 '21 at 14:36

It works making use of printf

{{ $host := trim $host }}
{{ $is_regexp := hasPrefix "~" $host }}
{{ $upstream_name := when $is_regexp (sha1 $host) $host }}
{{ $access_log := (or (and (not $.Env.DISABLE_ACCESS_LOGS) (printf "%s%s%s" "access_log /var/log/nginx/vhosts/" $host "_access.log vhost;")) "") }}

Concatenate variable in string

1 Answers1