fix: small error handling and test improvements

[mccutchen]

Plus a README update, just in case some poor soul stumbles across this repo and is tempted to use it for a real project.

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 77.60%. Comparing base (9a77e2f) to head (0d7b2c4).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
websocket.go	25.00%	6 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #9      +/-   ##
==========================================
- Coverage   78.70%   77.60%   -1.10%     
==========================================
  Files           2        2              
  Lines         385      393       +8     
==========================================
+ Hits          303      305       +2     
- Misses         60       64       +4     
- Partials       22       24       +2     

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