Refine CI workflow caching and dev as default make target

[pellared]

Reference: https://markphelps.me/2019/11/speed-up-your-go-builds-with-actions-cache/
Change dev as default Make target.

[codecov]

Codecov Report

Merging #120 (c40d1a2) into main (3d6cbcb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #120   +/-   ##
=======================================
  Coverage   50.00%   50.00%           
=======================================
  Files           1        1           
  Lines           2        2           
=======================================
  Hits            1        1           
  Misses          1        1           

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

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