ci: refactor codebase and update GitHub Actions workflow

- Remove Go version 1.20 from the GitHub Actions workflow

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Author: appleboy

.github/workflows/go.yml

@@ -31,7 +31,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
-        go: ["1.20", 1.21, 1.22, 1.23]
+        go: [1.21, 1.22, 1.23]
         include:
           - os: ubuntu-latest
             go-build: ~/.cache/go-build