fix: replace ioutil.readfile with os.readfile

[rfyiamcool]

summay

ioutil.ReadFile is Deprecated, As of Go 1.16, this function simply calls [os.ReadFile].

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (629990d) 69.99% compared to head (849b436) 70.20%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
conn.go	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #868      +/-   ##
==========================================
+ Coverage   69.99%   70.20%   +0.20%     
==========================================
  Files          11       11              
  Lines        1593     1594       +1     
==========================================
+ Hits         1115     1119       +4     
+ Misses        364      362       -2     
+ Partials      114      113       -1     

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