Update caching for dependencies in CI (#235)

Author: thomashoneyman

.github/workflows/ci.yml

@@ -31,16 +31,11 @@ jobs:
       - name: Cache dependencies
         uses: actions/cache@v2
         with:
-          path: |
-            ~/.stack
-            .stack-work
-          key: ${{ runner.os }}-stack-${{ hashFiles('stack.yaml.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-stack
+          path: ~/.stack
+          key: ${{ runner.os }}-stack-${{ hashFiles('stack.yaml.lock') }}-${{ hashFiles('trypurescript.cabal') }}
 
       - name: Build server code
-        run: |
-          stack --no-terminal -j1 build
+        run: stack --no-terminal -j1 build
 
       - name: Build server assets
         if: github.event_name == 'release'