Update lint rules, force testify/assert for tests

[Sean-Der]

Use testify's assert package instead of the standard library's testing package.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.84%. Comparing base (dd072ed) to head (bea8f43).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #776   +/-   ##
=======================================
  Coverage   78.84%   78.84%           
=======================================
  Files          41       41           
  Lines        5441     5441           
=======================================
  Hits         4290     4290           
  Misses        921      921           
  Partials      230      230           

Flag	Coverage Δ
go	78.84% <ø> (ø)
wasm	27.08% <ø> (ø)

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