CI: Update Haskell builds

.github/workflows/ci.yaml

@@ -1,6 +1,6 @@
 jobs:
   build:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: "actions/checkout@v1"
       - id: setup-haskell-cabal
@@ -9,20 +9,22 @@ jobs:
           cabal-version: "${{ matrix.cabal }}"
           enable-stack: false
           ghc-version: "${{ matrix.ghc }}"
-      - uses: "actions/cache@v1"
+      - name: Update Hackage repository
+        run: cabal update
+      - name: freeze
+        run: cabal freeze
+      - uses: "actions/cache@v2"
         with:
-          key: "${{ runner.os }}-${{ matrix.ghc }}-cabal"
-          path: "${{ steps.setup-haskell-cabal.outputs.cabal-store }}"
+          key: "${{ runner.os }}-${{ matrix.ghc }}-cabal-${{ hashFiles('cabal.project.freeze') }}"
+          path: "${{ steps.setup-haskell-cabal.outputs.cabal-store }} dist-newstyle"
       - name: Install dependencies
-        run: |
-          cabal update
-          cabal build --enable-tests --enable-benchmarks --only-dependencies
-      - name: build
-        run: cabal build --enable-tests --enable-benchmarks
-      - name: test
-        run: cabal test --enable-tests
-      - name: haddock
-        run: cabal haddock 
+        run: cabal build all --enable-tests --enable-benchmarks --only-dependencies
+      - name: build all
+        run: cabal build all --enable-tests --enable-benchmarks
+      - name: test all
+        run: cabal test all --enable-tests
+      - name: haddock all
+        run: cabal haddock all 
     strategy:
       matrix:
         cabal: