fix: crypto/rand.Read can't fail

[mccutchen]

Per the package docs:

Read calls io.ReadFull on Reader and crashes the program irrecoverably
if an error is returned. The default Reader uses operating system APIs
that are documented to never return an error on all but legacy Linux
systems.

[github-actions]

🔥 Run benchmarks comparing 2cdfb2a against main:

gh workflow run bench.yaml -f pr_number=71

Note: this comment will update with each new commit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.04%. Comparing base (91b0005) to head (2cdfb2a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #71      +/-   ##
==========================================
+ Coverage   98.11%   99.04%   +0.93%     
==========================================
  Files           2        2              
  Lines         425      421       -4     
==========================================
  Hits          417      417              
+ Misses          4        2       -2     
+ Partials        4        2       -2     

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