actions: update which go versions we test with

bump to 1.x and 1.14.x, the two most recent major go versions.  Also add
go1.11 on linux, which should still work, but is not actually supported.

.github/workflows/tests.yml

@@ -7,26 +7,35 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.x, 1.13.x]
+        go-version:
+          # support the two most recent major go versions
+          - 1.x
+          - 1.14.x
         platform: [ubuntu-latest, windows-latest]
+        include:
+          # minimum go version that works. This is not necessarily supported in
+          # any way, and will be bumped up without notice as needed.  But it at
+          # least lets us know what go version should work.
+          - go-version: 1.11
+            platform: ubuntu-latest
     runs-on: ${{ matrix.platform }}
 
     steps:
-    - uses: actions/setup-go@v1
-      with:
-        go-version: ${{ matrix.go-version }}
-    - uses: actions/checkout@v2
+      - uses: actions/setup-go@v1
+        with:
+          go-version: ${{ matrix.go-version }}
+      - uses: actions/checkout@v2
 
-    - name: Cache go modules
-      uses: actions/cache@v1
-      with:
-        path: ~/go/pkg/mod
-        key: ${{ runner.os }}-go-${{ hashFiles('go.sum') }}
-        restore-keys: ${{ runner.os }}-go-
+      - name: Cache go modules
+        uses: actions/cache@v1
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('go.sum') }}
+          restore-keys: ${{ runner.os }}-go-
 
-    - name: Run go test
-      run: go test -v -race -coverprofile coverage.txt -covermode atomic ./...
+      - name: Run go test
+        run: go test -v -race -coverprofile coverage.txt -covermode atomic ./...
 
-    - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v1
-      timeout-minutes: 2
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v1
+        timeout-minutes: 2