Cache node_modules in CI

.github/workflows/tests.yml

@@ -3,7 +3,7 @@ name: Node.js CI
 on: [push]
 
 jobs:
-  test:
+  build:
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -15,6 +15,15 @@ jobs:
       uses: actions/setup-node@v1
       with:
         node-version: ${{ matrix.node-version }}
+    - name: Cache node modules
+      uses: actions/cache@v1
+      with:
+        path: ~/.npm
+        key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
+        restore-keys: |
+          ${{ runner.os }}-build-${{ env.cache-name }}-
+          ${{ runner.os }}-build-
+          ${{ runner.os }}-
     - run: npm install
     - run: nohup npm run server &
       env: