Bump Go from 1.19 to 1.20

Bump the version of Go used in our GitHub Actions configuration to the
latest stable Go release.

.github/workflows/build.yml

@@ -32,7 +32,7 @@ jobs:
           # There is no expectation for actual Go code so we disable caching as
           # it relies on the existence of a go.sum file.
           cache: false
-          go-version: "1.19"
+          go-version: "1.20"
       - name: Lookup Go cache directory
         id: go-cache
         run: |