Docker Images with Ko

Since v1.15

You can also use ko to build and publish Docker container images.

Please notice that ko will build your binary again. That shouldn't increase the release times too much, as it'll use the same build options as the build pipe when possible, so the results will probably be cached.

Warning

Ko only runs on the publishing phase, so it might be a bit hard to test — you might need to push to a fake repository (or a fake tag) when playing around with its configuration.

# .goreleaser.yaml
kos:
-
  # ID of this image.
  id: foo

  # Build ID that should be used to import the build settings.
  build: build-id

  # Main path to build.
  # It must be a relative path
  #
  # Default: build.main
  main: ./cmd/...

  # Working directory used to build.
  #
  # Default: build.dir
  working_dir: .

  # Base image to publish to use.
  #
  # Default: 'cgr.dev/chainguard/static'
  base_image: alpine

  # Labels for the image.
  #
  # Since: v1.17
  labels:
    foo: bar

  # Repository to push to.
  #
  # Default: $KO_DOCKER_REPO
  repository: ghcr.io/foo/bar

  # Platforms to build and publish.
  #
  # Default: 'linux/amd64'
  platforms:
  - linux/amd64
  - linux/arm64

  # Tag to build and push.
  # Empty tags are ignored.
  #
  # Default: 'latest'
  # Templates: allowed
  tags:
  - latest
  - '{{.Tag}}'
  - '{{if not .Prerelease}}stable{{end}}'

  # Creation time given to the image
  # in seconds since the Unix epoch as a string.
  #
  # Since: v1.17
  # Templates: allowed
  creation_time: '{{.CommitTimestamp}}'

  # Creation time given to the files in the kodata directory
  # in seconds since the Unix epoch as a string.
  #
  # Since: v1.17
  # Templates: allowed
  ko_data_creation_time: '{{.CommitTimestamp}}'

  # SBOM format to use.
  #
  # Default: 'spdx'
  # Valid options are: spdx, cyclonedx, go.version-m and none.
  sbom: none

  # Ldflags to use on build.
  #
  # Default: build.ldflags
  ldflags:
  - foo
  - bar

  # Flags to use on build.
  #
  # Default: build.flags
  flags:
  - foo
  - bar

  # Env to use on build.
  #
  # Default: build.env
  env:
  - FOO=bar
  - SOMETHING=value


  # Bare uses a tag on the $KO_DOCKER_REPO without anything additional.
  bare: true

  # Whether to preserve the full import path after the repository name.
  preserve_import_paths: true

  # Whether to use the base path without the MD5 hash after the repository name.
  base_import_paths: true

Refer to ko's project page for more information.

Example

Here's a minimal example:

# .goreleaser.yml
before:
  hooks:
    - go mod tidy

builds:
  - env: [ "CGO_ENABLED=1" ]
    binary: test
    goos:
    - darwin
    - linux
    goarch:
    - amd64
    - arch64

kos:
  - repository: ghcr.io/caarlos0/test-ko
    tags:
    - '{{.Version}}'
    - latest
    bare: true
    preserve_import_paths: false
    platforms:
    - linux/amd64
    - linux/arm64

This will build the binaries for linux/arm64, linux/amd64, darwin/amd64 and darwin/arm64, as well as the Docker images and manifest for Linux.

Signing KO manifests

KO will add the built manifest to the artifact list, so you can sign them with docker_signs:

# .goreleaser.yml
docker_signs:
  -
    artifacts: manifests