Stop testing on EOL'd Go versions

Author: oschwald

.github/workflows/go.yml

@@ -8,7 +8,7 @@ jobs:
     name: Build
     strategy:
       matrix:
-        go-version: [1.9.x, 1.10.x, 1.11.x, 1.12.x, 1.13.x, 1.14.x]
+        go-version: [1.13.x, 1.14.x]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps: