test: enrich unit tests for pkg/protocol/request.go

[BaiZe1998]

What type of PR is this?

test

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.

Translate the PR title into Chinese.

为补充 pkg/protocol/request.go 单测

(Optional) More detail description for this PR(en: English/zh: Chinese).

en: ut coverage 51.31% -> 85.3%
zh: 单测覆盖率 51.31% -> 85.3%

Which issue(s) this PR fixes:

Part of #257

[codecov]

Codecov Report

Base: 61.57% // Head: 63.09% // Increases project coverage by +1.52% 🎉

Coverage data is based on head (83de078) compared to base (b7ff4bb).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #285      +/-   ##
===========================================
+ Coverage    61.57%   63.09%   +1.52%     
===========================================
  Files           84       84              
  Lines         8288     8288              
===========================================
+ Hits          5103     5229     +126     
+ Misses        2831     2701     -130     
- Partials       354      358       +4     

Impacted Files	Coverage Δ
pkg/common/compress/compress.go	80.95% <0.00%> (-2.86%)	⬇️
pkg/protocol/uri.go	87.06% <0.00%> (+0.63%)	⬆️
pkg/protocol/header.go	56.33% <0.00%> (+0.65%)	⬆️
pkg/protocol/request.go	83.24% <0.00%> (+31.93%)	⬆️

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[welkeyever]

lgtm, thx!