ci: update Go workflow to support latest versions only

- Remove Go version 1.18 and 1.19 from the workflow
- Update the Go versions to only include 1.20, 1.21, and 1.22
- Delete macOS job configuration and go-build cache path

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

.github/workflows/go.yml

@@ -27,12 +27,10 @@ jobs:
     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: