perf: reduce lo.Mode allocations

[NathanBaulch]

Fixes #733.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.22%. Comparing base (4e2c33e) to head (7899bad).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #734      +/-   ##
==========================================
+ Coverage   94.19%   94.22%   +0.03%     
==========================================
  Files          18       18              
  Lines        2806     2806              
==========================================
+ Hits         2643     2644       +1     
+ Misses        149      148       -1     
  Partials       14       14              

Flag	Coverage Δ
unittests	94.22% <100.00%> (+0.03%)	⬆️

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