Need help with templatating

Traefik Traefik v3 (latest)
1

I have several machines that expose a Syncthing endpoint, which I would like to route through Traefik. The target URL is of the form http://{{ $host }}.funny-name.ts.net:8384.

I wanted to template the configuration because all are identical, except for the hostname. I tried

{{ define "routers" }}
        {{ $host := . }}
        syncthing-{{ $host }}:
            rule: Host(`{{ $host }}.my-domain.eu`)
            service: syncthing-{{ $host }}
{{ end }}

{{ define "services" }}
        {{ $host := . }}
        syncthing-{{ $host }}:
            loadBalancer:
                servers:
                    - url: http://{{ $host }}.funny-name.ts.net:8384
{{ end }}

http:
    routers:
{{ template "routers" "aaa" "bbb" }}
    services:
{{ template "services" "aaa" "bbb" }}

I was expecting the followig configuration to be generated:

http:
    routers:
        syncthing-aaa:
            rule: Host(`aaa.my-domain.eu`)
            service: syncthing-aaa
       syncthing-bbb:
            rule: Host(`bbb.my-domain.eu`)
            service: syncthing-bbb
    services:
        syncthing-aaa:
            loadBalancer:
                servers:
                    - url: http://aaa.funny-name.ts.net:8384
         syncthing-bbb:
            loadBalancer:
                servers:
                    - url: http://bbb.funny-name.ts.net:8384

What I get instead is an error in the log (as soon as the file is updated)

traefik-1   | 2025-02-21T10:22:05+01:00 ERR Error occurred during watcher callback error="/config/config.d/testemplate.yaml: template: :18:22: executing \"\" at <\"aaa\">: can't give argument to non-function \"aaa\"" providerName=file
traefik-1   | 2025-02-21T10:22:05+01:00 ERR Error occurred during watcher callback error="/config/config.d/testemplate.yaml: template: :18:22: executing \"\" at <\"aaa\">: can't give argument to non-function \"aaa\"" providerName=file

What does this error mean and how to fix my template?

2

According to doc, Traefik uses go templating. Maybe you can find some validation tools and playgrounds for testing on the web.