add logger of session

[chenxuey]

每个 session 也可以注入一个日志

[codecov-io]

Codecov Report

Merging #1283 into master will decrease coverage by 0.06%.
The diff coverage is 36.76%.

@@            Coverage Diff             @@
##           master    #1283      +/-   ##
==========================================
- Coverage   57.36%   57.29%   -0.07%     
==========================================
  Files          44       44              
  Lines        7817     7824       +7     
==========================================
- Hits         4484     4483       -1     
- Misses       2777     2783       +6     
- Partials      556      558       +2

Impacted Files	Coverage Δ
session_convert.go	22.29% <0%> (ø)	⬆️
session_get.go	75.83% <100%> (ø)	⬆️
session_context.go	75% <100%> (ø)	⬆️
session_delete.go	58.22% <100%> (ø)	⬆️
session_schema.go	59.12% <100%> (ø)	⬆️
session_insert.go	56.84% <14.28%> (ø)	⬆️
session_update.go	56.44% <18.18%> (ø)	⬆️
session.go	57.9% <25%> (-0.59%)	⬇️
session_raw.go	57.57% <50%> (ø)	⬆️
session_find.go	67.91% <62.5%> (ø)	⬆️
... and 1 more

---

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[BetaCat0]

Please add some tests for this change :)