Not sure.
What happens if you try the plugins/versioninfo method?
Make a Caddy folder (anywhere) and put this inside in a main.go:
package main
import (
"github.com/mholt/caddy/caddy/caddymain"
// plug in plugins here, for example:
// _ "import/path/here"
)
func main() {
// optional: disable telemetry
// caddymain.EnableTelemetry = false
caddymain.Run()
}
Then run go mod init caddy and go build.