CI: add GH Actions workflow for linux unit tests

Signed-off-by: Mayank Shah <mayankshah1614@gmail.com>

.github/workflows/darwin.yaml

@@ -0,0 +1,20 @@
+name: Darwin
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+jobs:
+  build:
+    name: Unit Tests
+    runs-on: macos-latest
+    steps:
+    - name: Set up Go 1.x
+      uses: actions/setup-go@v2
+      with:
+        go-version: ^1.13
+      id: go
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v2
+    - name: Run unit tests
+      run: go test -v -race ./pkg/...