Switch to support older go 1.18

[cedric-appdirect]

This resolve issue #6

[codecov-commenter]

Codecov Report

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@@            Coverage Diff            @@
##             master       #8   +/-   ##
=========================================
  Coverage          ?   77.29%           
=========================================
  Files             ?        2           
  Lines             ?      229           
  Branches          ?        0           
=========================================
  Hits              ?      177           
  Misses            ?       35           
  Partials          ?       17           

Flag	Coverage Δ
go-	75.98% <0.00%> (?)
go-1.18	77.29% <0.00%> (?)
go-1.19	77.29% <0.00%> (?)
go-1.20	75.98% <0.00%> (?)
go-1.21	75.98% <0.00%> (?)
macos-latest	75.98% <0.00%> (?)
ubuntu-latest	77.29% <0.00%> (?)

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[appleboy]

@cedric-appdirect Thanks.