Added support for GitHub actions (#4)

.github/workflows/build.yml

@@ -0,0 +1,27 @@
+name: build
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go: [1.14, 1.15, 1.16]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Setup Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go }}
+      - name: Build
+        run: |
+          go vet ./...
+          go test -v ./...
+          go build ./...

go.mod

@@ -0,0 +1,4 @@
+module github.com/dgrijalva/jwt-go
+
+go 1.14
+