Update tests.yml to use go1.16

[bmoffatt]

It's time

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[codecov-io]

Codecov Report

Merging #363 (c2050c8) into master (e60bf50) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #363   +/-   ##
=======================================
  Coverage   72.22%   72.22%           
=======================================
  Files          19       19           
  Lines         738      738           
=======================================
  Hits          533      533           
  Misses        138      138           
  Partials       67       67           

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