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Neil O'Toole edited this page Mar 15, 2020 · 35 revisions

xcgo is a maximalist Docker image for cross-compiling and releasing/distributing CGo-enabled Go/Golang applications. At this time, it can build and dist macOS, Windows and Linux CGo projects for arch amd64.

xcgo has what gophers crave:

  • go 1.14
  • OSX SDK Catalina / macOS 10.15
  • docker
  • snapcraft
  • goreleaser
  • golangci-lint
  • mage
  • zsh and oh-my-zsh
  • and a bunch of other stuff.

The primary source of documentation for xcgo is the wiki. Start there. There's a companion example project (neilotoole/sqlitr) that was created explicitly to exhibit xcgo: it demonstrates pretty much the entire array of xcgo's capabilities, showing how to release to brew, scoop, snap, Docker Hub, GitHub, etc. The neilotoole/xcgo images are published to Docker Hub.

Note: No effort has yet been made to provide support for other archs such as 386 (or for an OS beyond the typical three), but pull requests are welcome. Note also that no effort has been made to make this image slim. xcgo by mission is maximalist (it's a 3GB+ image), but I'm sure the Dockerfile can be slimmed down. Again, pull requests are welcome.

Usage

You can test xcgo with:

$ docker run -it neilotoole/xcgo:latest go version
go version go1.14 linux/amd64

To play around in the container, launch into a shell:

$ docker run -it neilotoole/xcgo:latest zsh

xcgo doesn't prescribe a particular usage approach. Some possibilities:

  • Launch a container shell session, clone your repo, and build (or even edit and do all your work) within the container.
  • Mount your local repo into the container, shell in, and build from within the container.
  • With local repo mounted, invoke xcgo with goreleaser: this is pretty typical.

Let's look at a few of these approaches:

Example: go build inside container

From inside the docker container, we'll build (amd64) binaries for macOS, Linux, and Windows.

$ git clone https://github.com/neilotoole/sqlitr.git && cd sqlitr
$ GOOS=darwin GOARCH=amd64 CC=o64-clang CXX=o64-clang++ go build -o dist/darwin_amd64/sqlitr
$ GOOS=linux GOARCH=amd64 go build -o dist/linux_amd64/sqlitr
$ GOOS=windows GOARCH=amd64 CC=x86_64-w64-mingw32-gcc CXX=x86_64-w64-mingw32-g++ go build -o dist/windows_amd64/sqlitr.exe

You should end up with something like this:

$ tree ./dist
./dist
├── darwin_amd64
│   └── sqlitr
├── linux_amd64
│   └── sqlitr
└── windows_amd64
    └── sqlitr.exe

Running file on each of the binaries:

./dist/darwin_amd64/sqlitr: Mach-O 64-bit x86_64 executable, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL>
./dist/linux_amd64/sqlitr: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/l, for GNU/Linux 3.2.0, BuildID[sha1]=9a130449828e21fc5ef935582d889bba0344432c, not stripped
./dist/windows_amd64/sqlitr.exe: PE32+ executable (console) x86-64, for MS Windows

Note that the linux binary listed above is dynamically linked. There are additional steps you can take to statically link instead (useful if you're distributing on an Alpine image for example). See sqlitr .goreleaser.yml build_linux section.

Example: goreleaser

Quite possibly you'll want to use xcgo in conjunction with goreleaser.

Again, we'll use sqlitr to demonstrate. On your local machine, clone the sqlitr repo, mount it into the xcgo container and run goreleaser.

$ git clone https://github.com/neilotoole/sqlitr.git && cd sqlitr
$ docker run --rm --privileged \
-v $(pwd):/go/src/github.com/neilotoole/sqlitr \
-v /var/run/docker.sock:/var/run/docker.sock \
-w /go/src/github.com/neilotoole/sqlitr \
neilotoole/xcgo:latest goreleaser --snapshot --rm-dist

The above will build that CGo project via goreleaser with binaries for macOS, Linux, and Windows.

$ tree ./dist                                                                           130   master
./dist
├── build_linux_linux_amd64
│   └── sqlitr
├── build_macos_darwin_amd64
│   └── sqlitr
├── build_windows_windows_amd64
│   └── sqlitr.exe
├── checksums.txt
├── config.yaml
├── goreleaserdocker393975300
│   ├── Dockerfile
│   ├── LICENSE
│   ├── README.md
│   ├── sqlitr
│   └── testdata
│       └── example.sqlite
├── sqlitr_v0.1.23-snapshot_darwin_amd64.tar.gz
├── sqlitr_v0.1.23-snapshot_linux_amd64
│   └── prime
│       ├── meta
│       │   └── snap.yaml
│       └── sqlitr
├── sqlitr_v0.1.23-snapshot_linux_amd64.deb
├── sqlitr_v0.1.23-snapshot_linux_amd64.rpm
├── sqlitr_v0.1.23-snapshot_linux_amd64.snap
├── sqlitr_v0.1.23-snapshot_linux_amd64.tar.gz
└── sqlitr_v0.1.23-snapshot_windows_amd64.zip

The above example uses goreleaser --snapshot. To actually publish artifacts (brew, scoop, snap, dockerhub, etc), you need to inject appropriate secrets into the xcgo container. In this next example we pass secrets for GitHub, docker, and snapcraft.

Note that this example actually won't succeed for you (as you don't have the secrets)

docker run --rm --privileged \
-v $(pwd):/go/src/github.com/neilotoole/sqlitr \
-v /var/run/docker.sock:/var/run/docker.sock \
-e "GITHUB_TOKEN=$GITHUB_TOKEN" \
-e "DOCKER_USERNAME=$DOCKER_USERNAME" -e "DOCKER_PASSWORD=$DOCKER_PASSWORD" -e "DOCKER_REGISTRY=$DOCKER_REGISTRY" \
-v "${HOME}/.snapcraft.login":/.snapcraft.login \
-w /go/src/github.com/neilotoole/sqlitr \
neilotoole/xcgo:latest goreleaser --rm-dist

Again, see the neilotoole/sqlitr example project for more.

Parameterization

Some params that can be passed to xcgo (as args to docker run):

  • Docker: -e DOCKER_USERNAME=X -e DOCKER_PASSWORD=X

    When present, xcgo's entrypoint.sh performs a docker login. Supply -e DOCKER_REGISTRY=X to use a registry other than Docker Hub.

  • GitHub: -e GITHUB_TOKEN=X or -e GORELEASER_GITHUB_TOKEN=X

    Used to publish artifacts to GitHub (e.g. by goreleaser).

  • Snapcraft: -v "${HOME}/.snapcraft.login":/.snapcraft.login

    When /.snapcraft.login is present in the xcgo container, entrypoint.sh performs a snapcraft login. This enables uses of snapcraft, e.g. by goreleaser to publish a snap. Supply -e SNAPCRAFT_LOGIN_FILE=/other/place/.snapcraft.login to specify an alternative mount location for the login file. See the wiki for more.