Test CI cache problem

Check if we have only one matrix combination, if the cache problem remains.

.github/workflows/tests.yaml

@@ -24,7 +24,7 @@ jobs:
         # version must be string, otherwise it will be converted to float
         # and the trailing zero will be removed. 1.20 -> 1.2
         go-version: [ "1.21" ]
-        postgres-version: [ 16, 15, 14, 13, 12, 11 ]
+        postgres-version: [ 16 ]
     # Ensure that all combinations of Go and Postgres versions will run
     continue-on-error: true
 
@@ -72,9 +72,9 @@ jobs:
           path: |
             ~/.cache/go-build
             ~/go/pkg/mod
-          key: ${{ runner.os }}}-${{ matrix.go-version }}-${{ matrix.postgres-version }}-go-${{ hashFiles('**/go.sum') }}
+          key: ${{ runner.os }}}-go-${{ matrix.go-version }}-postgres-${{ matrix.postgres-version }}-${{ hashFiles('**/go.sum') }}
           restore-keys: |
-            ${{ runner.os }}-go-
+            ${{ runner.os }}-go-${{ matrix.go-version }}-
 
       # Runs Go tests
       - name: test