Use fmt.Errorf to be able to unwrap error

[johejo]

Also includes minor refactorings

And added a workflow file for github actions.

Should I delete the .travis.yml and badges?

[codecov-io]

Codecov Report

Merging #46 (3136567) into master (2c8720d) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #46   +/-   ##
=======================================
  Coverage   90.27%   90.27%           
=======================================
  Files           2        2           
  Lines         185      185           
=======================================
  Hits          167      167           
  Misses         13       13           
  Partials        5        5           

Impacted Files	Coverage Δ
shellwords.go	89.59% <100.00%> (ø)
util_posix.go	100.00% <100.00%> (ø)

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[mattn]

LGTM

[mattn]

Thanks