Bump Golang to 1.15

[vania-pooh]

No description provided.

[codecov]

Codecov Report

Merging #55 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #55   +/-   ##
=======================================
  Coverage   54.89%   54.89%           
=======================================
  Files           3        3           
  Lines         235      235           
=======================================
  Hits          129      129           
  Misses         92       92           
  Partials       14       14           

Flag	Coverage Δ
#go	54.89% <ø> (ø)

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