Go (a.k.a., Golang)

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Go (golang) is a general purpose, higher-level, imperative programming language.

GitHub repo: https://github.com/docker-library/golang

Library reference

This content is imported from the official Docker Library docs, and is provided by the original uploader. You can view the Docker Store page for this repo at https://store.docker.com/images/golang.

Supported tags and respective Dockerfile links

For detailed information about the published artifacts of each of the above supported tags (image metadata, transfer size, etc), please see the repos/golang directory in the docker-library/repo-info GitHub repo.

For more information about this image and its history, please see the relevant manifest file (library/golang). This image is updated via pull requests to the docker-library/official-images GitHub repo.

What is Go?

Go (a.k.a., Golang) is a programming language first developed at Google. It is a statically-typed language with syntax loosely derived from C, but with additional features such as garbage collection, type safety, some dynamic-typing capabilities, additional built-in types (e.g., variable-length arrays and key-value maps), and a large standard library.

wikipedia.org/wiki/Go_(programming_language)

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How to use this image

Start a Go instance in your app

The most straightforward way to use this image is to use a Go container as both the build and runtime environment. In your Dockerfile, writing something along the lines of the following will compile and run your project:

FROM golang:1.6-onbuild

This image includes multiple ONBUILD triggers which should cover most applications. The build will COPY . /go/src/app, RUN go get -d -v, and RUN go install -v.

This image also includes the CMD ["app"] instruction which is the default command when running the image without arguments.

You can then build and run the Docker image:

$ docker build -t my-golang-app .
$ docker run -it --rm --name my-running-app my-golang-app

Note: the default command in golang:onbuild is actually go-wrapper run, which includes set -x so the binary name is printed to stderr on application startup. If this behavior is undesirable, then adding CMD ["app"] (or CMD ["myapp"] if a Go custom import path is in use) will silence it by running the built binary directly.

Compile your app inside the Docker container

There may be occasions where it is not appropriate to run your app inside a container. To compile, but not run your app inside the Docker instance, you can write something like:

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 go build -v

This will add your current directory as a volume to the container, set the working directory to the volume, and run the command go build which will tell go to compile the project in the working directory and output the executable to myapp. Alternatively, if you have a Makefile, you can run the make command inside your container.

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash -c make

Cross-compile your app inside the Docker container

If you need to compile your application for a platform other than linux/amd64 (such as windows/386):

$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp -e GOOS=windows -e GOARCH=386 golang:1.6 go build -v

Alternatively, you can build for multiple platforms at once:

$ docker run --rm -it -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash
$ for GOOS in darwin linux; do
>   for GOARCH in 386 amd64; do
>     go build -v -o myapp-$GOOS-$GOARCH
>   done
> done

Image Variants

The golang images come in many flavors, each designed for a specific use case.

golang:<version>

This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of. This tag is based off of buildpack-deps. buildpack-deps is designed for the average user of docker who has many images on their system. It, by design, has a large number of extremely common Debian packages. This reduces the number of packages that images that derive from it need to install, thus reducing the overall size of all images on your system.

golang:onbuild

This image makes building derivative images easier. For most use cases, creating a Dockerfile in the base of your project directory with the line FROM golang:onbuild will be enough to create a stand-alone image for your project.

While the onbuild variant is really useful for “getting off the ground running” (zero to Dockerized in a short period of time), it’s not recommended for long-term usage within a project due to the lack of control over when the ONBUILD triggers fire (see also docker/docker#5714, docker/docker#8240, docker/docker#11917).

Once you’ve got a handle on how your project functions within Docker, you’ll probably want to adjust your Dockerfile to inherit from a non-onbuild variant and copy the commands from the onbuild variant Dockerfile (moving the ONBUILD lines to the end and removing the ONBUILD keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your Dockerfile as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-ONBUILD steps).

golang:alpine

This image is based on the popular Alpine Linux project, available in the alpine official image. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.

This variant is highly recommended when final image size being as small as possible is desired. The main caveat to note is that it does use musl libc instead of glibc and friends, so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn’t have an issue with this, so this variant is usually a very safe choice. See this Hacker News comment thread for more discussion of the issues that might arise and some pro/con comparisons of using Alpine-based images.

To minimize image size, it’s uncommon for additional related tools (such as git or bash) to be included in Alpine-based images. Using this image as a base, add the things you need in your own Dockerfile (see the alpine image description for examples of how to install packages if you are unfamiliar).

golang:windowsservercore

This image is based on Windows Server Core (microsoft/windowsservercore). As such, it only works in places which that image does, such as Windows 10 Professional/Enterprise (Anniversary Edition) or Windows Server 2016.

For information about how to get Docker running on Windows, please see the relevant “Quick Start” guide provided by Microsoft:

License

View license information for the software contained in this image.

Supported Docker versions

This image is officially supported on Docker version 17.04.0-ce.

Support for older versions (down to 1.6) is provided on a best-effort basis.

Please see the Docker installation documentation for details on how to upgrade your Docker daemon.

User Feedback

Issues

If you have any problems with or questions about this image, please contact us through a GitHub issue. If the issue is related to a CVE, please check for a cve-tracker issue on the official-images repository first.

You can also reach many of the official image maintainers via the #docker-library IRC channel on Freenode.

Contributing

You are invited to contribute new features, fixes, or updates, large or small; we are always thrilled to receive pull requests, and do our best to process them as fast as we can.

Before you start to code, we recommend discussing your plans through a GitHub issue, especially for more ambitious contributions. This gives other contributors a chance to point you in the right direction, give you feedback on your design, and help you find out if someone else is working on the same thing.

Documentation

Documentation for this image is stored in the golang/ directory of the docker-library/docs GitHub repo. Be sure to familiarize yourself with the repository’s README.md file before attempting a pull request.

library, sample, Go, Golang