Run tests on all platforms

Author: muan

.github/workflows/nodejs.yml

@@ -6,19 +6,18 @@ on:
     - master
 jobs:
   build:
-
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
 
     strategy:
       matrix:
-        node-version: [8.x, 10.x, 12.x]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
     - uses: actions/checkout@v1
-    - name: Use Node.js ${{ matrix.node-version }}
+    - name: Use Node.js 12.x
       uses: actions/setup-node@v1
       with:
-        node-version: ${{ matrix.node-version }}
+        node-version: 12.x
     - name: npm install, build, and test
       run: |
         npm install