feat: custom env by options.env

[fengmk2]

closes #106

refactor: generator to async await

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +6.15 🎉

Comparison is base (5420a47) 86.38% compared to head (2dcaa06) 92.54%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #107      +/-   ##
==========================================
+ Coverage   86.38%   92.54%   +6.15%     
==========================================
  Files          14       15       +1     
  Lines        1991     1999       +8     
  Branches      287      329      +42     
==========================================
+ Hits         1720     1850     +130     
+ Misses        271      149     -122     

Impacted Files	Coverage Δ
lib/agent_worker.js	100.00% <100.00%> (ø)
lib/app_worker.js	100.00% <100.00%> (+8.20%)	⬆️
lib/master.js	97.41% <100.00%> (+8.71%)	⬆️
lib/utils/messenger.js	98.36% <100.00%> (+3.27%)	⬆️
lib/utils/mode/impl/worker_threads/app.js	74.72% <100.00%> (ø)
lib/utils/options.js	90.47% <100.00%> (+0.47%)	⬆️
lib/utils/terminate.js	97.46% <100.00%> (+40.50%)	⬆️
lib/utils/timer.js	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes

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