Add GitHub actions to build master and each PR

.github/workflows/go.yml

@@ -0,0 +1,37 @@
+name: Go build for Linux
+on: [push, pull_request]
+jobs:
+
+  build:
+    name: Build
+    runs-on: ubuntu-18.04
+    steps:
+
+    - name: Set up Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: 1.12
+      id: go
+
+    - name: Check out repository
+      uses: actions/checkout@v2
+
+    - name: Linux build
+      run: |
+        make
+
+    - name: Upload Linux build
+      uses: actions/upload-artifact@v2
+      with:
+        name: linux-amd64
+        path: |
+          doh-client/doh-client
+          doh-server/doh-server
+
+    - name: Cache
+      uses: actions/cache@v2
+      with:
+        # A directory to store and save the cache
+        path: ~/go/pkg/mod
+        # An explicit key for restoring and saving the cache
+        key: ${{ runner.os }}-${{ hashFiles('**/go.sum') }}