Example multi-arch Dockerfile for Go projects

Dockerfile

FROM --platform=${BUILDPLATFORM:-linux/amd64} golang:1.16 as builder

ARG TARGETPLATFORM
ARG BUILDPLATFORM
ARG TARGETOS
ARG TARGETARCH

WORKDIR /app/
ADD . .
RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-w -s" -o yourapplication main.go

FROM --platform=${TARGETPLATFORM:-linux/amd64} scratch
WORKDIR /app/
COPY --from=builder /app/yourapplication /app/yourapplication
ENTRYPOINT ["/app/yourapplication"]

Makefile

.DEFAULT_GOAL := default

IMAGE ?= yourapplication:latest

export DOCKER_CLI_EXPERIMENTAL=enabled

.PHONY: build # Build the container image
build:
	@docker buildx create --use --name=crossplat --node=crossplat && \
	docker buildx build \
		--output "type=docker,push=false" \
		--tag $(IMAGE) \
		.

.PHONY: publish # Push the image to the remote registry
publish:
	@docker buildx create --use --name=crossplat --node=crossplat && \
	docker buildx build \
		--platform linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64,linux/ppc64le,linux/s390x \
		--output "type=image,push=true" \
		--tag $(IMAGE) \
		.

I might be wrong, but according to docker docs BUILDPLATFORM should be defined as ARG before the first FROM too.
https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact

It's been a while since I looked at this but I have this setup in one of my projects that is working at least when it last built a couple years ago - https://github.com/AverageMarcus/kube-image-prefetch/blob/master/Dockerfile

You're correct, sorry, these args are defined by docker. When I declared them before FROM, they became empty. Thanks for this example, helped me a lot.

I’m so glad to hear that! 😁

@AverageMarcus I am trying to understand from your above Makefile what is the difference between build and publish as both looks pretty same except platform difference.

@cherrymu The --output is what makes the difference.

--output "type=image,push=true" 

This instructs the command to push to the remote registry whereas this..

--output "type=docker,push=false"

...just builds the image on the local machine.

Thanks @AverageMarcus for clarifying it