Use a test matrix with the last three stable Go versions (#96)

.github/workflows/go.yml

@@ -7,26 +7,33 @@ on:
     branches: [ master ]
 
 jobs:
-  build:
-    name: Build
+  test:
+    name: Test
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go: [ "1.16", "1.17", "1.18" ]
     steps:
-    - name: Check out
-      uses: actions/checkout@v2
+      - uses: actions/checkout@v2
 
-    - name: Setup Go
-      uses: actions/setup-go@v2
+      - uses: actions/setup-go@v2
         with:
-        go-version: ^1.17
+          go-version: ${{ matrix.go }}
+          check-latest: true
 
       - name: Build
         run: go build -v ./...
 
       - name: Test
+        if: ${{ matrix.go != '1.16' }}
         run: go test -v -coverprofile=coverage.txt -shuffle on ./...
 
+      - name: Test
+        if: ${{ matrix.go == '1.16' }}
+        run: go test -v -coverprofile=coverage.txt ./...
+
       - name: Coverage
-      uses: codecov/codecov-action@v1.0.13
+        uses: codecov/codecov-action@v2
 
   lint:
     name: Lint