Cross-Compiling Go Application Images with buildx

#go #docker

This article was originally published on bmf-tech.com.

Overview

I felt the need to cross-compile the image of an application I am developing privately (due to differences in architecture between the local development environment and the production environment), so I made some notes.

buildx

Docker Desktop comes with buildx by default, so I will use that.

Docker Buildx

Using buildx makes it easy to create multi-architecture compatible images.

Example

Assuming there is a Dockerfile like this (it's actually the Dockerfile I use...)

FROM --platform=$BUILDPLATFORM golang:1.20.0-alpine as builder

WORKDIR /go/gobel-api/app

ARG TARGETPLATFORM
ARG BUILDPLATFORM
ARG TARGETOS
ARG TARGETARCH

COPY . .

RUN apk update && \
    apk upgrade && \
    apk add --no-cache libc-dev gcc git openssh openssl bash

RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -o app

FROM --platform=$TARGETPLATFORM alpine

COPY --from=builder /go/gobel-api/app ./

ENTRYPOINT ["/app"]

For environment variables, refer to the following.
cf. https://matsuand.github.io/docs.docker.jp.onthefly/engine/reference/builder/

Building and pushing looks like this. You can specify multiple platforms.

// Create builder instance
docker buildx create --name buildx-builder
docker buildx use buildx-builder

// Build and push to dockerhub
docker buildx build --no-cache --push --platform linux/amd64,linux/arm64 --file app/Dockerfile --tag bmfsan/gobel-api app/