If you're using [GitHub secrets](https://docs.github.com/en/actions/security-guides/encrypted-secrets)
and need to handle multi-line value, you will need to place the key-value pair
between quotes:

```yaml
secrets: |
  "MYSECRET=${{ secrets.GPG_KEY }}"
  GIT_AUTH_TOKEN=abcdefghi,jklmno=0123456789
  "MYSECRET=aaaaaaaa
  bbbbbbb
  ccccccccc"
  FOO=bar
  "EMPTYLINE=aaaa

  bbbb
  ccc"
  "JSON_SECRET={""key1"":""value1"",""key2"":""value2""}"
```

| Key              | Value                               |
| ---------------- | ----------------------------------- |
| `MYSECRET`       | `***********************`           |
| `GIT_AUTH_TOKEN` | `abcdefghi,jklmno=0123456789`       |
| `MYSECRET`       | `aaaaaaaa\nbbbbbbb\nccccccccc`      |
| `FOO`            | `bar`                               |
| `EMPTYLINE`      | `aaaa\n\nbbbb\nccc`                 |
| `JSON_SECRET`    | `{"key1":"value1","key2":"value2"}` |

> [!NOTE]
>
> Double escapes are needed for quote signs.

## SSH mounts

SSH mounts let you authenticate with SSH servers.
For example to perform a `git clone`,
or to fetch application packages from a private repository.

The following Dockerfile example uses an SSH mount
to fetch Go modules from a private GitHub repository.

```dockerfile {collapse=1}
# syntax=docker/dockerfile:1

ARG GO_VERSION="{{% param example_go_version %}}"

FROM golang:${GO_VERSION}-alpine AS base
ENV CGO_ENABLED=0
ENV GOPRIVATE="github.com/foo/*"
RUN apk add --no-cache file git rsync openssh-client
RUN mkdir -p -m 0700 ~/.ssh && ssh-keyscan github.com >> ~/.ssh/known_hosts
WORKDIR /src

FROM base AS vendor
# this step configure git and checks the ssh key is loaded
RUN --mount=type=ssh <<EOT
  set -e
  echo "Setting Git SSH protocol"
  git config --global url."git@github.com:".insteadOf "https://github.com/"
  (
    set +e
    ssh -T git@github.com
    if [ ! "$?" = "1" ]; then
      echo "No GitHub SSH key loaded exiting..."
      exit 1
    fi
  )
EOT
# this one download go modules
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=ssh \
    go mod download -x

FROM vendor AS build
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=cache,target=/root/.cache \
    go build ...
```

To build this Dockerfile, you must specify an SSH mount that the builder can
use in the steps with `--mount=type=ssh`.

The following GitHub Action workflow uses the `MrSquaare/ssh-setup-action`
third-party action to bootstrap SSH setup on the GitHub runner. The action
creates a private key defined by the GitHub Action secret `SSH_GITHUB_PPK` and
adds it to the SSH agent socket file at `SSH_AUTH_SOCK`. The SSH mount in the
build step assume `SSH_AUTH_SOCK` by default, so there's no need to specify the
ID or path for the SSH agent socket explicitly.

{{< tabs >}}
{{< tab name="`docker/build-push-action`" >}}

```yaml
name: ci

on:
  push:

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Set up SSH
        uses: MrSquaare/ssh-setup-action@2d028b70b5e397cf8314c6eaea229a6c3e34977a # v3.1.0
        with:
          host: github.com
          private-key: ${{ secrets.SSH_GITHUB_PPK }}
          private-key-name: github-ppk

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          ssh: default
          push: true
          tags: user/app:latest
```

{{< /tab >}}
{{< tab name="`docker/bake-action`" >}}

```yaml
name: ci

on:
  push:

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      - name: Set up SSH
        uses: MrSquaare/ssh-setup-action@2d028b70b5e397cf8314c6eaea229a6c3e34977a # v3.1.0
        with:
          host: github.com
          private-key: ${{ secrets.SSH_GITHUB_PPK }}
          private-key-name: github-ppk

      - name: Build
        uses: docker/bake-action@v6
        with:
          set: |
            *.ssh=default
```

{{< /tab >}}
{{< /tabs >}}