Update go version to 1.18

[youyuanwu]

Fix ci lint issues

[codecov]

Codecov Report

Merging #153 (b012b50) into master (625cad1) will not change coverage.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##           master     #153   +/-   ##
=======================================
  Coverage   90.73%   90.73%           
=======================================
  Files          22       22           
  Lines        2979     2979           
=======================================
  Hits         2703     2703           
  Misses        224      224           
  Partials       52       52           

Impacted Files	Coverage Δ
example_validator.go	83.06% <ø> (ø)
helpers.go	82.24% <0.00%> (ø)
spec.go	87.43% <ø> (ø)
spec_messages.go	71.15% <ø> (ø)
default_validator.go	87.62% <100.00%> (ø)
schema.go	100.00% <100.00%> (ø)
validator.go	98.72% <100.00%> (ø)
values.go	99.30% <100.00%> (ø)