Retain environment variable when loading key from config

[jribbink]

closes #79

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.

Project coverage is 44.00%. Comparing base (61b6da5) to head (a1b6bb2).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
accounts/keys.go	77.77%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
+ Coverage   43.82%   44.00%   +0.18%     
==========================================
  Files          40       40              
  Lines        3366     3384      +18     
==========================================
+ Hits         1475     1489      +14     
- Misses       1631     1634       +3     
- Partials      260      261       +1     

Flag	Coverage Δ
unittests	44.00% <77.77%> (+0.18%)	⬆️

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