Add matrix to GitHub workflow

[pellared]

Why

It is good to ensure that the build works on different environments.
Solves #68

What

Refine the GitHub workflow to work with multiple versions of OS and Go.

[codecov]

Codecov Report

Merging #105 (9198ad5) into master (91723e0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #105   +/-   ##
=======================================
  Coverage   50.00%   50.00%           
=======================================
  Files           1        1           
  Lines           2        2           
=======================================
  Hits            1        1           
  Misses          1        1           

Flag	Coverage Δ
Linux	50.00% <ø> (?)
Windows	50.00% <ø> (?)
macOS	50.00% <ø> (?)

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