Force Go 1.20 in CI

Author: colin969

.github/workflows/nexus.yml

@@ -21,6 +21,9 @@ jobs:
           auth_header="$(git config --local --get http.https://github.com/.extraheader)"
           git submodule sync --recursive
           git -c "http.extraheader=$auth_header" -c protocol.version=2 submodule update --init --force --recursive --depth=1
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.20.14'
       - name: Build
         env:
           GOOS: "windows"