Unable to build with docker (caddy-docker-proxy) plugin

[kpine]

Not sure if this is an unsupported plugin, but the following fails to build:

$ docker pull abiosoft/caddy:builder
builder: Pulling from abiosoft/caddy
Digest: sha256:305e08cea6537ff651262d8a9c9fa1676b4f71dee96fa84f91352b3789a9d5b9
Status: Image is up to date for abiosoft/caddy:builder
docker.io/abiosoft/caddy:builder

$ docker run --rm -v /tmp/caddy:/install -e PLUGINS=docker abiosoft/caddy:builder

starting stage: fetching caddy source
Cloning into '/go/src/github.com/caddyserver/caddy'...
Note: checking out 'bff2469d9d76ba5924f6d9affcf60bf44dcfa06c'.

<snip>

starting stage: customising plugins and telemetry
go: creating new go.mod: module caddy
go: finding github.com/caddyserver/caddy v1.0.3
<snip>
go: finding github.com/lucaslorentz/caddy-docker-proxy/plugin latest
go: finding github.com/lucaslorentz/caddy-docker-proxy v0.3.1
go: downloading github.com/lucaslorentz/caddy-docker-proxy v0.3.1
go: extracting github.com/lucaslorentz/caddy-docker-proxy v0.3.1
<snip>

starting stage: building caddy
go: downloading gopkg.in/natefinch/lumberjack.v2 v2.0.0
go: downloading github.com/russross/blackfriday v0.0.0-20170610170232-067529f716f4
go: downloading github.com/gorilla/websocket v1.4.0
<snip>
go: finding github.com/gopherjs/gopherjs v0.0.0-20181017120253-0766667cb4d1
go: finding github.com/google/go-cmp v0.2.0
go: error loading module requirements
error at 'building caddy'

I can provide the full log if needed. I am able to download a custom binary including the plugin from the caddy home page, as well as build from the caddy-docker-proxy project.

[riker09]

I believe I'm having the same issue.

can't load package: package caddy:
docker.go:2:10: invalid import path: ""
error at 'building caddy'

[Daemonslayer2048]

I am having this issue too has anyone fixed this?