github: Update Go versions

Author: bep

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.18.x,1.19.x,1.20.x]
+        go-version: [1.19.x,1.20.x,1.21.x]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps: