nextcloud-docs/golang/content.md

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)

%%LOGO%%

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 %%REPO%%: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