Tool builder: gcr.io/cloud-builders/go

This Cloud Build builder runs the go tool.

When to use this builder

The gcr.io/cloud-builders/go build step should be used when you want to run the go tool directly on your source, similar to how a developer uses the go tool locally to build (go build or go install), test (go test), or manage source (go get or go generate).

alpine vs debian

There are two supported versions of this builder, one for alpine and one for debian. The difference is significant since, by default, Go dynamically links libc. Binaries built in an alpine environment don't always work in a debian-like (including ubuntu, etc) environment, or vice versa.

The specific versions are available as

• gcr.io/cloud-builders/go:alpine
• gcr.io/cloud-builders/go:debian

And gcr.io/cloud-builders/go:latest is an alias for gcr.io/cloud-builders/go:alpine.

Workspace setup

Before the go tool is used, the build step first sets up a workspace.

To determine the workspace structure, this tool checks the following, in order:

1. Is $GOPATH set? Use that.
2. Is there a ./src directory? Set GOPATH=$PWD.
3. Is $PROJECT_ROOT set? Make a temporary workspace in GOPATH=./gopath, and link the contents of the current directory into ./gopath/src/$PROJECT_ROOT/*.
4. Does a .go file in the current directory have a comment like // import "$PROJECT_ROOT"? Use the $PROJECT_ROOT found in the import comment instead of a provided $PROJECT_ROOT environment variable.

Once the workspace is set up, the args to the build step are passed through to the go tool.

This tool builder sets CGO_ENABLED=0, so that all binaries are linked statically.

Output files

The binaries built by a go install step will be available to subsequent build steps.

If you use the install subcommand, the binaries will end up in $GOPATH/bin.

• If you set $GOPATH, the binaries will end up in $GOPATH/bin.
• If you rely on ./src to indicate the workspace, the binaries will end up in ./bin.
• If you use $PROJECT_ROOT or an //import comment, the binaries will end up in ./gopath/bin.

Examples

• Hello, World! is a basic example that builds a binary that is injected into a container image. It uses the $PROJECT_ROOT method to define its workspace.
• Whole workspace is the same as the "Hello, World!" example, except that it uses the ./src method to define its workspace.

Building this builder

To build this builder, run the following command in this directory.

$ gcloud builds submit . --config=cloudbuild.yaml