Switch from Travis-CI to GitHub actions (#1286)

Travis-CI is dead. GitHub actions is the new hotness.
The minimally supported version is Go1.11 to make use of modules.

.github/workflows/test.yml

@@ -0,0 +1,22 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x]
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v2
+      with:
+        go-version: ${{ matrix.go-version }}
+    - name: Checkout code
+      uses: actions/checkout@v2
+    - name: TestLatest
+      if: matrix.go-version == '1.16.x'
+      run: ./test.bash
+    - name: TestAll
+      if: matrix.go-version != '1.16.x'
+      run: go test ./...