fix: wait 5s when master exit

[popomore]

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

Merging #60 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
+ Coverage   98.28%   98.29%   +<.01%     
==========================================
  Files           7        7              
  Lines         408      410       +2     
==========================================
+ Hits          401      403       +2     
  Misses          7        7

Impacted Files	Coverage Δ
lib/master.js	98.31% <100%> (+0.01%)	⬆️

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[popomore]

eggjs/bin#88

[atian25]

1.16.0