Shut down server safely on SIGINT/TERM. Fixes #21

[lkysow]

No description provided.

[codecov-io]

Codecov Report

Merging #215 into master will decrease coverage by 0.39%.
The diff coverage is 0%.

@@           Coverage Diff            @@
##           master    #215     +/-   ##
========================================
- Coverage    63.9%   63.5%   -0.4%     
========================================
  Files          39      39             
  Lines        1748    1759     +11     
========================================
  Hits         1117    1117             
- Misses        581     592     +11     
  Partials       50      50

Impacted Files	Coverage Δ
server/server.go	72.3% <0%> (-3.94%)	⬇️

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