Update golang:1.12.7-stretch Docker digest to 5ed856d

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
golang	docker	digest	88e108f -> 5ed856d

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[codecov-io]

Codecov Report

Merging #25 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #25   +/-   ##
=======================================
  Coverage   72.34%   72.34%           
=======================================
  Files           1        1           
  Lines          94       94           
=======================================
  Hits           68       68           
  Misses         15       15           
  Partials       11       11

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