fix: refactoring code of graceful exits

[luhaoling]

🔍 What type of PR is this?

👀 What this PR does / why we need it:

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

🅰 Which issue(s) this PR fixes:

Fixes #1886

📝 Special notes for your reviewer:

🎯 Describe how to verify it

📑 Additional documentation e.g., RFC, notion, Google docs, usage docs, etc.:

[codecov]

Codecov Report

Attention: 85 lines in your changes are missing coverage. Please review.

Comparison is base (760fbc9) 5.32% compared to head (ce83799) 5.32%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
pkg/common/startrpc/start.go	4.54%	42 Missing ⚠️
internal/msggateway/n_ws_server.go	0.00%	28 Missing ⚠️
pkg/util/genutil/genutil.go	0.00%	10 Missing ⚠️
internal/msggateway/init.go	0.00%	4 Missing ⚠️
internal/tools/cron_task.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #1885      +/-   ##
========================================
- Coverage   5.32%   5.32%   -0.01%     
========================================
  Files         43      43              
  Lines       3830    3852      +22     
========================================
+ Hits         204     205       +1     
- Misses      3613    3634      +21     
  Partials      13      13              

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[AndrewZuo01]

could you fix go-lint error？