opt: use worker pool for asynchronous tasks on Windows

[panjf2000]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 55.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 78.75%. Comparing base (2f1bf9b) to head (5f2d2a4).
Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
connection_windows.go	55.00%	8 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #657      +/-   ##
==========================================
- Coverage   78.82%   78.75%   -0.08%     
==========================================
  Files          21       21              
  Lines        2546     2551       +5     
==========================================
+ Hits         2007     2009       +2     
- Misses        420      422       +2     
- Partials      119      120       +1     

Flag	Coverage Δ
unittests	78.75% <55.00%> (-0.08%)	⬇️

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