chore: update CI configuration and supported Go versions

- Update golangci-lint-action version from v4 to v6
- Remove Go version 1.18 and 1.19 from the supported versions
- Remove macOS build configuration and cache settings

Signed-off-by: Bo-Yi Wu <[email protected]>

.github/workflows/go.yml

@@ -21,19 +21,17 @@ jobs:
           go-version-file: "go.mod"
 
       - name: Setup golangci-lint
-        uses: golangci/golangci-lint-action@v4
+        uses: golangci/golangci-lint-action@v6
         with:
           args: --verbose
   test:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        go: [1.18, 1.19, "1.20", 1.21, 1.22]
+        go: ["1.20", 1.21, 1.22]
         include:
           - os: ubuntu-latest
             go-build: ~/.cache/go-build
-          - os: macos-latest
-            go-build: ~/Library/Caches/go-build
     name: ${{ matrix.os }} @ Go ${{ matrix.go }}
     runs-on: ${{ matrix.os }}
     env: