feat: support active subgenerator

[nikewu]

support active subgenerator

[codecov-io]

Codecov Report

Merging #93 into master will decrease coverage by 0.3%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #93      +/-   ##
==========================================
- Coverage   93.75%   93.44%   -0.31%     
==========================================
  Files          11       11              
  Lines         304      305       +1     
  Branches       38       38              
==========================================
  Hits          285      285              
- Misses         19       20       +1

Impacted Files	Coverage Δ
lib/core/index.js	75.67% <0%> (-1.04%)	⬇️

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[cpselvis]

OK