fix: highlight IsCA

[shipengqi]

Thank you for contributing to golib!

Please add a summary of your change

fix: highlight IsCA

Does your change fix a particular issue?

Fixes #(issue)

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[codecov-commenter]

Codecov Report

Merging #40 (c653065) into main (c213045) will increase coverage by 0.17%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   71.54%   71.72%   +0.17%     
==========================================
  Files          22       22              
  Lines         970      976       +6     
==========================================
+ Hits          694      700       +6     
  Misses        200      200              
  Partials       76       76              

Flag	Coverage Δ
unittests	71.72% <100.00%> (+0.17%)	⬆️

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Files Changed	Coverage Δ
crtutil/tmpl/funcs.go	67.36% <100.00%> (+1.17%)	⬆️
crtutil/tmpl/template.go	78.57% <100.00%> (+0.52%)	⬆️

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