fix, improve and add ut

[qicosmos]

No description provided.

[codecov-commenter]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (3a99afb) 65.05% compared to head (5e3c5bd) 65.22%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #436      +/-   ##
==========================================
+ Coverage   65.05%   65.22%   +0.17%     
==========================================
  Files         217      217              
  Lines       13297    13365      +68     
==========================================
+ Hits         8650     8717      +67     
- Misses       4647     4648       +1     

Files	Coverage Δ
include/cinatra/coro_http_connection.hpp	94.84% <ø> (ø)
include/cinatra/websocket.hpp	82.75% <80.00%> (+1.19%)	⬆️
tests/test_coro_http_server.cpp	85.41% <89.28%> (+1.65%)	⬆️

... and 9 files with indirect coverage changes

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