Fix Go version mismatch - use stable Go 1.23

The issue was that Go 1.25.x is not yet available in GitHub Actions.
Updated:
- go.mod: go 1.25.1 → go 1.23
- CI workflow: Use 1.23.x for all jobs (test, lint, format)
- Removed 1.24.x and 1.25.x from test matrix

This should resolve the golangci-lint failures caused by Go version issues.

Author: leifj

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.23.x', '1.24.x', '1.25.x']
+        go-version: ['1.23.x']
 
     steps:
     - name: Checkout code
@@ -48,7 +48,7 @@ jobs:
     
     - name: Upload coverage to Codecov
       uses: codecov/codecov-action@v4
-      if: matrix.go-version == '1.25.x'
+      if: matrix.go-version == '1.23.x'
       with:
         files: ./coverage.out
         flags: unittests
@@ -67,7 +67,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        go-version: '1.25.x'
+        go-version: '1.23.x'
 
     - name: golangci-lint
       uses: golangci/golangci-lint-action@v4
@@ -87,7 +87,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v5
       with:
-        go-version: '1.25.x'
+        go-version: '1.23.x'
 
     - name: Check formatting
       run: |

go.mod

@@ -1,3 +1,3 @@
 module github.com/sirosfoundation/go-spocp
 
-go 1.25.1
+go 1.23