Keep reusing caches from previous runs for copilot runs (#1390)

Author: jakebailey

.github/actions/setup-go/action.yml

@@ -8,6 +8,9 @@ inputs:
   cache-name:
     description: Name of scoped cache for this set up.
     default: 'cache'
+  cache-from-previous-run:
+    description: Use the cache from the previous run if available.
+    default: 'false'
 
 runs:
   using: composite
@@ -19,15 +22,37 @@ runs:
         go-version: ${{ inputs.go-version }}
         cache: false
 
+    # There is more code downloaded and built than is covered by '**/go.sum',
+    # so give each job its own cache to try and not end up sharing the wrong
+    # cache between jobs, and hash the Herebyfile and golancgi-lint version.
+
+    # In cache-from-previous-run mode, we try to restore the cache from the
+    # previous run, and force the next cache to be saved by keying it on the
+    # run ID.
+
+    - name: Create Go cache keys
+      id: go-cache-keys
+      shell: bash
+      run: |
+        if [[ "$CACHE_FROM_PREVIOUS_RUN" == "true" ]]; then
+          echo "key=$PREFIX-$CACHE_NAME-$RUN_ID" >> $GITHUB_OUTPUT
+          echo "restore-keys=$PREFIX-$CACHE_NAME" >> $GITHUB_OUTPUT
+        else
+          echo "key=$PREFIX-$CACHE_NAME" >> $GITHUB_OUTPUT
+          echo "restore-keys=$PREFIX" >> $GITHUB_OUTPUT
+        fi
+
+      env:
+        PREFIX: ts-setup-go-${{ runner.os }}-${{ steps.install-go.outputs.go-version }}-${{ hashFiles('**/go.sum', '**/Herebyfile.mjs', '**/.custom-gcl.yml') }}-${{ github.workflow }}
+        CACHE_NAME: ${{ inputs.cache-name }}
+        RUN_ID: ${{ github.run_id }}
+        CACHE_FROM_PREVIOUS_RUN: ${{ inputs.cache-from-previous-run }}
+
     - name: Go cache
       uses: actions/cache@5a3ec84eff668545956fd18022155c47e93e2684 # v4.2.3
       with:
-        # There is more code downloaded and built than is covered by '**/go.sum',
-        # so give each job its own cache to try and not end up sharing the wrong
-        # cache between jobs.
-        key: ts-setup-go-${{ runner.os }}-${{ steps.install-go.outputs.go-version }}-${{ hashFiles('**/go.sum', '**/Herebyfile.mjs', '**/.custom-gcl.yml') }}-${{ github.workflow }}-${{ inputs.cache-name }}
-        restore-keys: |
-          ts-setup-go-${{ runner.os }}-${{ steps.install-go.outputs.go-version }}-${{ hashFiles('**/go.sum', '**/Herebyfile.mjs', '**/.custom-gcl.yml') }}
+        key: ${{ steps.go-cache-keys.outputs.key }}
+        restore-keys: ${{ steps.go-cache-keys.outputs.restore-keys }}
         path: |
           ~/go/pkg/mod
           ~/.cache/go-build

.github/workflows/copilot-setup-steps.yml

@@ -26,6 +26,7 @@ jobs:
           # Updated to 1.25.0-rc.1 to improve compilation time
           go-version: '>=1.25.0-rc.1'
           cache-name: copilot-setup-steps
+          cache-from-previous-run: 'true'
       - run: npm i -g @playwright/mcp@0.0.28
       - run: npm ci
       # pull dprint caches before network access is blocked