ci: Fix build caching on Windows (#4811)

* ci: Fix build caching on Windows

I was getting tired of Windows being slow as molasses in our CI jobs, so I went to look at our trusty source of github actions + golang information, and found a somewhat recent commit that actually fixed it. See mvdan/github-actions-golang@4b75472

I'll do a 2nd empty commit to re-trigger CI shortly to confirm that it actually fixes it.

* Retrigger CI

.github/workflows/ci.yml

@@ -78,12 +78,20 @@ jobs:
         printf "Git version: $(git version)\n\n"
         # Calculate the short SHA1 hash of the git commit
         echo "::set-output name=short_sha::$(git rev-parse --short HEAD)"
-        echo "::set-output name=go_cache::$(go env GOCACHE)"
 
     - name: Cache the build cache
       uses: actions/cache@v2
       with:
-        path: ${{ steps.vars.outputs.go_cache }}
+        # In order:
+        # * Module download cache
+        # * Build cache (Linux)
+        # * Build cache (Mac)
+        # * Build cache (Windows)
+        path: |
+          ~/go/pkg/mod
+          ~/.cache/go-build
+          ~/Library/Caches/go-build
+          ~\AppData\Local\go-build
         key: ${{ runner.os }}-${{ matrix.go }}-go-ci-${{ hashFiles('**/go.sum') }}
         restore-keys: |
           ${{ runner.os }}-${{ matrix.go }}-go-ci

.github/workflows/cross-build.yml

@@ -42,12 +42,16 @@ jobs:
           go env
           printf "\n\nSystem environment:\n\n"
           env
-          echo "::set-output name=go_cache::$(go env GOCACHE)"
 
       - name: Cache the build cache
         uses: actions/cache@v2
         with:
-          path: ${{ steps.vars.outputs.go_cache }}
+          # In order:
+          # * Module download cache
+          # * Build cache (Linux)
+          path: |
+            ~/go/pkg/mod
+            ~/.cache/go-build
           key: cross-build-go${{ matrix.go }}-${{ matrix.goos }}-${{ hashFiles('**/go.sum') }}
           restore-keys: |
             cross-build-go${{ matrix.go }}-${{ matrix.goos }}

.github/workflows/release.yml

@@ -56,7 +56,6 @@ jobs:
         env
         echo "::set-output name=version_tag::${GITHUB_REF/refs\/tags\//}"
         echo "::set-output name=short_sha::$(git rev-parse --short HEAD)"
-        echo "::set-output name=go_cache::$(go env GOCACHE)"
 
         # Add "pip install" CLI tools to PATH
         echo ~/.local/bin >> $GITHUB_PATH
@@ -91,7 +90,12 @@ jobs:
     - name: Cache the build cache
       uses: actions/cache@v2
       with:
-        path: ${{ steps.vars.outputs.go_cache }}
+        # In order:
+        # * Module download cache
+        # * Build cache (Linux)
+        path: |
+          ~/go/pkg/mod
+          ~/.cache/go-build
         key: ${{ runner.os }}-go${{ matrix.go }}-release-${{ hashFiles('**/go.sum') }}
         restore-keys: |
           ${{ runner.os }}-go${{ matrix.go }}-release