fix: pin go version to avoid test errors

Because I specified go >= 1.20, we were using go1.22.1 where
there's an os.fileWithoutWriteTo instead of *os.File.

.github/workflows/go.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v4
       with:
-        go-version: ">=1.20.6"
+        go-version: "1.20.14"
 
     - name: Build
       run: go build -v ./...

README.md

@@ -246,6 +246,8 @@ the `Request` and `Response` fields;
 
 - [ ] run `go get -u -v ./... && go mod tidy`;
 
+- [ ] make sure the Go version used by GitHub actions is correct;
+
 - [ ] commit the changes and push `merged-main` to gitub;
 
 - [ ] open a PR using this check-list as part of the PR text and merge it *using a merge commit*;