fix: update go version for unit testing

Author: matthiasmatt

.github/workflows/unit-tests.yml

@@ -12,7 +12,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v3
         with:
-          go-version: 1.19
+          go-version: 1.21
           cache: true
 
       - name: Run all unit tests.