Test against latest Go's

Author: y-yagi

.github/workflows/ci.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: [1.15, 1.16, 1.17]
+        go: [1.15, 1.16, 1.17, 1.18, 1.19]
     steps:
     - name: Set up Go
       uses: actions/setup-go@v2