allow to template dockerfile contents

[caarlos0]

refs https://github.com/orgs/goreleaser/discussions/3842#discussioncomment-6376551

[ryancurrah]

We have been using GoReleaser for building and releasing over 300 of our modules. It's been an exceptional tool in streamlining our CI/CD pipeline. Recently, we have encountered a challenge which we believe could be solved with an enhancement to GoReleaser.

Currently, we use a single Dockerfile across all our modules, where the binary/service name is injected as an environment variable SERVICENAME at runtime in the GoReleaser configuration. We use a shell to interpolate this path like /opt/acme/bin/${SERVICENAME}.

FROM docker.acme.com/service-go:22.04 AS base

ARG SERVICENAME
ENV SERVICENAME=${SERVICENAME}

COPY --chown="acme:acme" ${SERVICENAME} /opt/acme/bin/

EXPOSE 8443

ENTRYPOINT exec "/opt/acme/bin/${SERVICENAME}"

However, we have started an initiative to use minimal, shell-less containers for improved security and resource optimization. This presents a challenge as the current mechanism of using environment variables for path interpolation will no longer work, leading us towards creating a unique Dockerfile for each service, which isn't very efficient.

This feature would allow us to use template variables in the Dockerfile which would be replaced during the build process. A potential Dockerfile might look something like this:

FROM docker.acme.com/service-go:distroless11 AS base

COPY --chown="acme:acme" {{ .Artifacts[0].Binary }} /opt/acme/bin/

EXPOSE 8443

ENTRYPOINT ["/opt/acme/bin/{{ .Artifacts[0].Binary }}"]

[caarlos0]

that adds a lot of context, thanks for sharing @ryancurrah .

I'll work on this soon 🙏

[caarlos0]

will be on next pro release :)

PS: if you think of any more fields you'd need to template the contents, feel free to ping here or open more issues :)

[ryancurrah]

Thank you!