64 lines
2.9 KiB
Markdown
64 lines
2.9 KiB
Markdown
# What is Go?
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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.
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> [wikipedia.org/wiki/Go_(programming_language)](http://en.wikipedia.org/wiki/Go_%28programming_language%29)
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%%LOGO%%
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# How to use this image
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## Start a Go instance in your app
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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:
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```dockerfile
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FROM golang:1.6-onbuild
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```
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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`.
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This image also includes the `CMD ["app"]` instruction which is the default command when running the image without arguments.
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You can then build and run the Docker image:
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```console
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$ docker build -t my-golang-app .
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$ docker run -it --rm --name my-running-app my-golang-app
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```
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*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](https://golang.org/s/go14customimport) is in use) will silence it by running the built binary directly.
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## Compile your app inside the Docker container
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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:
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```console
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$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 go build -v
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```
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This will add your current directory as a volume to the container, set the working directory to the volume, and run the command `go build` which will tell go to compile the project in the working directory and output the executable to `myapp`. Alternatively, if you have a `Makefile`, you can run the `make` command inside your container.
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```console
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$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash -c make
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```
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## Cross-compile your app inside the Docker container
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If you need to compile your application for a platform other than `linux/amd64` (such as `windows/386`):
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```console
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$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp -e GOOS=windows -e GOARCH=386 golang:1.6 go build -v
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```
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Alternatively, you can build for multiple platforms at once:
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```console
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$ docker run --rm -it -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash
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$ for GOOS in darwin linux; do
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> for GOARCH in 386 amd64; do
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> go build -v -o myapp-$GOOS-$GOARCH
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> done
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> done
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```
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