refactor some lua code

[ElvinEfendi]

What this PR does / why we need it:
Refactors some Lua code.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

[ElvinEfendi]

/assign @aledbf

[codecov-io]

Codecov Report

Merging #2664 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2664      +/-   ##
==========================================
- Coverage    40.9%   40.84%   -0.06%     
==========================================
  Files          72       72              
  Lines        5073     5073              
==========================================
- Hits         2075     2072       -3     
- Misses       2716     2718       +2     
- Partials      282      283       +1

Impacted Files	Coverage Δ
cmd/nginx/main.go	22.62% <0%> (-2.19%)	⬇️

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[aledbf]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, ElvinEfendi

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