Update instructions for use_nixcached

README.md

@@ -19,11 +19,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Check out code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: Install Nix
-      uses: cachix/install-nix-action@v16
+      uses: cachix/install-nix-action@v23
     - name: Set up cache
-      uses: zombiezen/setup-nix-cache-action@v0.1.0
+      uses: zombiezen/setup-nix-cache-action@v0.3.0
       with:
         substituters: s3://example-bucket
         secret_keys: ${{ secrets.NIX_PRIVATE_KEY }}
@@ -33,8 +33,7 @@ jobs:
       run: nix-build
 ```
 
-Using a [Google Cloud Storage][] bucket for loading and storing
-with the [interoperability endpoint][]:
+Using a [Google Cloud Storage][] bucket for loading and storing:
 
 ```yaml
 name: Build
@@ -44,11 +43,43 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Check out code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
     - name: Install Nix
-      uses: cachix/install-nix-action@v16
+      uses: cachix/install-nix-action@v23
+    - name: Authenticate to Google Cloud Platform
+      # See https://github.com/google-github-actions/auth/blob/main/README.md
+      # for details on how to set up.
+      uses: google-github-actions/auth@v1
     - name: Set up cache
-      uses: zombiezen/setup-nix-cache-action@v0.1.0
+      uses: zombiezen/setup-nix-cache-action@v0.3.0
+      with:
+        substituters: gs://example-bucket
+        secret_keys: ${{ secrets.NIX_PRIVATE_KEY }}
+        use_nixcached: true
+    - name: Build
+      run: nix-build
+```
+
+The example above uses [nixcached][] to connect to Google Cloud Storage
+using normal service account credentials.
+If you prefer to avoid the dependency, you can instead use the [interoperability endpoint][],
+but you will have to generate an HMAC key:
+
+```yaml
+# Connecting to GCS without nixcached (not recommended).
+
+name: Build
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v4
+    - name: Install Nix
+      uses: cachix/install-nix-action@v23
+    - name: Set up cache
+      uses: zombiezen/setup-nix-cache-action@v0.3.0
       with:
         substituters: s3://example-bucket?endpoint=https://storage.googleapis.com
         secret_keys: ${{ secrets.NIX_PRIVATE_KEY }}
@@ -61,6 +92,7 @@ jobs:
 [Amazon Web Services S3]: https://aws.amazon.com/s3/
 [Google Cloud Storage]: https://cloud.google.com/storage
 [interoperability endpoint]: https://cloud.google.com/storage/docs/interoperability
+[nixcached]: https://github.com/zombiezen/nixcached
 
 ## Inputs
 
@@ -86,6 +118,11 @@ Access key ID for downloading and uploading artifacts
 
 Secret access key for downloading and uploading artifacts
 
+### `use_nixcached`
+
+If `true`, use [nixcached][] for uploading and downloading.
+This permits concurrent uploading and more straightforward authentication.
+
 ## License
 
 [Apache 2.0](LICENSE)