Add hidden field

[pei0804]

for #88

[codecov-io]

Codecov Report

Merging #89 into master will increase coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
+ Coverage   85.79%   85.89%   +0.09%     
==========================================
  Files           5        5              
  Lines         718      723       +5     
==========================================
+ Hits          616      621       +5     
  Misses         62       62              
  Partials       40       40

Impacted Files	Coverage Δ
parser.go	81.63% <100%> (+0.26%)	⬆️

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