Add min supported and two most recent Go versions to workflow

Author: jstemmer

.github/workflows/main.yml

@@ -9,12 +9,15 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go: [ '1.18', '1.17', '1.13' ]
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v3
         with:
-          go-version: 1.17
+          go-version: ${{ matrix.go }}
       - name: Build
         run: go build -v ./...
       - name: Test