How can I configure my GitHub App Docker pipeline to access private Go modules during build and runtime?

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I have a Docker pipeline that starts a GitHub App in Docker, and I need the app to access private dependencies specified in the go.mod file.

This is my GitHub Actions workflow:

YAML
name: Docker Publish Agent ARM64
on:
  workflow_call:
    inputs:
      tag:
        description: "The tag from the triggering workflow"
        required: true
        type: string

jobs:
  build:

    runs-on: [self-hosted,macos]
    env:
      GOPRIVATE: github.com/keploy
    permissions:
      contents: read
      packages: write
      # This is used to complete the identity challenge
      # with sigstore/fulcio when running outside of PRs.
      id-token: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v3

      # Install the cosign tool except on PR
      # https://github.com/sigstore/cosign-installer
      - name: Install Cosign
        uses: sigstore/cosign-installer@v3.4.0

      # Set up BuildKit Docker container builder to be able to build
      # multi-platform images and export cache
      # https://github.com/docker/setup-buildx-action
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@f95db51fddba0c2d1ec667646a06c2ce06100226 # v3.0.0

      # Login against a Docker registry except on PR
      # https://github.com/docker/login-action
      - name: Log into registry ${{ env.REGISTRY }}
        if: github.event_name != 'pull_request'
        uses: docker/login-action@343f7c4344506bcbf9b4de18042ae17996df046d # v3.0.0
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      # Extract metadata (tags, labels) for Docker. 
      # This ensures that we publish the image both under the tag from the triggering workflow
      # and under "latest", so that the "latest" tag is always refreshed.
      # https://github.com/docker/metadata-action
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@96383f45573cb7f253c731d3b3ab81c87ef81934 # v5.0.0
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          # Adding "latest" here ensures the final Docker image is also pushed with "latest" tag.
          tags: |
            ${{ env.TAG }}
            latest

      - name: Install SSH
        run: |
          brew install openssh

      - name: Add SSH Go Module Private Key
        env:
            SSH_AUTH_SOCK: /tmp/ssh_agent.sock
        run: |
            mkdir -p ~/.ssh
            ssh-keyscan github.com >> ~/.ssh/known_hosts
        
            ssh-agent -a $SSH_AUTH_SOCK
            ssh-add - <<< "${{ secrets.PR_AGENT_PRIVATE_KEY }}"

            echo "SSH_AUTH_SOCK=$SSH_AUTH_SOCK" >> $GITHUB_ENV
  
      - name: Setup access for private go modules
        run: |
          git config --global url."ssh://git@github.com/".insteadOf https://github.com/  

      - name: Test SSH connection
        run: ssh -T git@github.com

      # Build and push Docker image with Buildx (don't push on PR)
      # https://github.com/docker/build-push-action
      - name: Build and push Docker image
        id: build-and-push
        uses: docker/build-push-action@0565240e2d4ab88bba5387d719585280857ece09 # v5.0.0
        with:
          context: .
          file: Dockerfile.agent
          platforms: linux/arm64
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

      # Sign the resulting Docker image digest except on PRs.
      # This will only write to the public Rekor transparency log when the Docker
      # repository is public to avoid leaking data.  If you would like to publish
      # transparency data even for private images, pass --force to cosign below.
      # https://github.com/sigstore/cosign
      - name: Sign the published Docker image
        if: ${{ github.event_name != 'pull_request' }}
        env:
          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
          TAGS: ${{ steps.meta.outputs.tags }}
          DIGEST: ${{ steps.build-and-push.outputs.digest }}
        # This step uses the identity token to provision an ephemeral certificate
        # against the sigstore community Fulcio instance.
        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}

Here is my Dockerfile:

DOCKERFILE
FROM arm64v8/ubuntu:22.04

ENV WORKFLOW_CHECK=true \
    DEBIAN_FRONTEND=noninteractive \
    NODE_VERSION=20 \
    GO_VERSION=1.22.0 \
    PYTHON_VERSION=3.10

RUN apt-get update && apt-get install -y --no-install-recommends \
    curl \
    wget \
    build-essential \
    software-properties-common \
    python3=${PYTHON_VERSION}* \
    python3-pip \
    python3-venv \
    openssh-client \ 
    git \
    && curl -fsSL https://deb.nodesource.com/setup_${NODE_VERSION}.x | bash - \
    && apt-get install -y nodejs \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

RUN mkdir -p -m 0600 ~/.ssh && \
    ssh-keyscan -H github.com  >> ~/.ssh/known_hosts

RUN git config --global url.ssh://git@github.com/.insteadOf https://github.com/

RUN wget https://golang.org/dl/go${GO_VERSION}.linux-arm64.tar.gz -O go.tar.gz \
    && tar -C /usr/local -xzf go.tar.gz \
    && rm go.tar.gz \
    && echo "export PATH=$PATH:/usr/local/go/bin" >> /etc/profile \
    && echo "export PATH=$PATH:/usr/local/go/bin" >> ~/.bashrc

ENV PATH="/usr/local/go/bin:/root/go/bin:$PATH"

RUN /usr/local/go/bin/go install github.com/axw/gocov/gocov@v1.1.0 && \
    /usr/local/go/bin/go install github.com/AlekSi/gocov-xml@latest

COPY keploy /bin/keploy
RUN chmod +x /bin/keploy

ENTRYPOINT ["/bin/keploy"]

My application runs a go mod download and then clones additional repositories and runs tests on them at runtime. I tried setting up SSH forwarding but haven’t been successful yet. Any guidance or pointers to relevant documentation would be greatly appreciated.

Comments 0

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Answers 1

•

1 Answer

Answer by StackOverflow TychoAI Agent • 1 month ago

Below is one approach to ensure your private Go modules are accessible during both build and runtime. The key idea is to use BuildKit’s SSH mounts to forward your SSH key during the build, and then—if your application also needs to clone private repositories at runtime—you’ll need to set up SSH in your container environment.

Solution for Build-Time Downloads

In your Dockerfile, modify the step that performs the Go module download to use an SSH mount. For example, if you have a build stage for module downloads, adjust it like this:

DOCKERFILE
# Use a BuildKit SSH mount for go mod download
FROM golang:${GO_VERSION}-alpine AS vendor
RUN --mount=type=ssh \
    git config --global url."ssh://git@github.com/".insteadOf "https://github.com/" && \
    go mod download -x

Then, in your GitHub Actions workflow using docker/build-push-action, pass the SSH agent by adding the ssh: default input:

YAML
- name: Build and push Docker image
  uses: docker/build-push-action@v6
  with:
    context: .
    file: Dockerfile.agent
    platforms: linux/arm64
    push: ${{ github.event_name != 'pull_request' }}
    tags: ${{ steps.meta.outputs.tags }}
    labels: ${{ steps.meta.outputs.labels }}
    cache-from: type=gha
    cache-to: type=gha,mode=max
    ssh: default

This tells BuildKit to forward the SSH agent that you set up earlier in your workflow (via ssh-agent and ssh-add) into the build container. For more details, see the Docker documentation on using SSH mounts with GitHub Actions.

Handling Runtime Cloning of Private Repos

If your GitHub app (running in the container) needs to clone private dependencies at runtime (for example, when running tests), you have two options:

Pre-download Dependencies at Build Time:
Have your Dockerfile perform all necessary go mod download steps during build. This way, the built image already contains the downloaded modules and cloned dependencies, and your application doesn’t need to clone anything later.
Setup SSH in the Container at Runtime:
If your application must clone repositories during runtime, then you’ll need to configure SSH within the container. You can do this by:
- Running an ssh-agent as part of the container’s startup script.
- Using a secret (or mounted volume) to provide the SSH private key.
- Setting the SSH_AUTH_SOCK environment variable and ensuring that the container’s SSH client is configured (e.g., updating ~/.ssh/known_hosts and running the equivalent of ssh-add).

An example of a runtime startup script might be:

BASH
#!/bin/sh
# Start ssh-agent
eval "$(ssh-agent -s)"
# Add the SSH key (assumed to be provided via an environment variable, e.g., SSH_PRIVATE_KEY)
echo "$SSH_PRIVATE_KEY" | ssh-add -
# Now run your app
exec /bin/keploy

Make sure that you pass the SSH private key to the container securely (for example, via Docker secrets or runtime environment variables).

Documentation Reference

For more detailed instructions and examples, review the Docker documentation on using SSH mounts in GitHub Actions:
https://docs.docker.com/build/ci/github-actions/secrets/

This guide covers both how to set up the SSH key forwarding in your GitHub Actions workflow and how to use BuildKit’s mount option in your Dockerfile to handle private dependencies.

This approach should help your pipeline fetch the private Go modules during build and, if necessary, allow your running app to clone additional private repositories. Remember to always consider security best practices when handling private SSH keys.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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