添加缓存模块的单元测试用例

[sunist-c]

这个PR将为 #4 添加单元测试用例，包括：

1. 内存缓存实现 - 缓存接口的单元测试
2. Redis缓存实现 - 缓存接口的单元测试
3. 内存缓存实现 - 计数器接口的单元测试
4. Redis缓存实现 - 计数器接口的单元测试

此外，还更新了GitHub Actions的配置，在PullRequest时开启了CI工作流

[codecov]

Codecov Report

Attention: 232 lines in your changes are missing coverage. Please review.

Comparison is base (c598f1e) 30.82% compared to head (26e5deb) 57.16%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #5       +/-   ##
===========================================
+ Coverage   30.82%   57.16%   +26.34%     
===========================================
  Files          27       30        +3     
  Lines        1687     2351      +664     
===========================================
+ Hits          520     1344      +824     
+ Misses       1096      843      -253     
- Partials       71      164       +93     

Files	Coverage Δ
cache/redis/driver.go	78.78% <83.33%> (ø)
cache/memory/implement.go	90.00% <80.00%> (+84.94%)	⬆️
cache/memory/errors.go	63.15% <62.50%> (+63.15%)	⬆️
cache/memory/accessor.go	83.13% <83.28%> (+72.93%)	⬆️
cache/redis/accessor.go	51.86% <50.58%> (ø)

... and 2 files with indirect coverage changes