chore(ci): upgrade minimum Go version to 1.25

- Update go directive to 1.25.0 in go.mod and example go.mod
- Remove Go 1.24 from CI test matrix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: appleboy

.github/workflows/testing.yml

@@ -33,7 +33,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        go: [1.24, 1.25]
+        go: [1.25]
         include:
           - os: ubuntu-latest
             go-build: ~/.cache/go-build