Update build.yml

.github/workflows/build.yml

@@ -42,6 +42,14 @@ jobs:
       - uses: actions/setup-dotnet@v1
         with:
           dotnet-version: '5.0.x'
+  
+      - name: Nuget Cache
+        uses: actions/cache@v2
+        with:
+          path: ~/.nuget/packages
+          key: ${{ runner.os }}-nuget-${{ hashFiles('**/packages.lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-nuget
 
       - name: Run Unit Tests
         run: |