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Go Defer-Recover Is Awesome

1 min read

Lessons Learned From A Browser Based Go Test Driver

The following is not news to experienced Go developers but it was to me.

I hadn't written a Go web server app before, so going in it seemed simple. Then things started to go wrong. I learned that the Go runtime supports a form a recovery that many other runtimes don't.

  1. Defer-Recover is the best thing going for a server app
    • read more about it here
    • something most conventional runtimes don't support
    • Go allows recovery from panics, and even syntax errors in tests
    • in a node.js server app,for example, the recovery strategy is typically to let the process die and have it auto restarted
    • in a Go program, you can use defer-recover to catch panics and possibly continue
    • for example, if one web handler is crashing because some resource is missing, you can do a deferred recovery, log something and potentially disable the handler, while letting the rest of the program continue
    • or, just do a comprehensive log and restart
  2. Go native testing works as though tests are compiled at runtime
    • syntax errors don't show up until a test is run
    • with a syntax error, output will not be what you expect
    • using a deferred recovery you can continue and log information even after a syntax error in a test
  3. all tests should probably have a deferred recovery procedure to catch panics
    • a panic in a test won't kill the whole test sequence, just that test. it will be marked Fail
    • with a deferred recovery you can log why the panic occurred instead of a cryptic fail message
  4. a simple web server may not be so simple
    • see the rules for handler patterns
    • '/' will handle anything starting with '/'
    • longer patterns are checked first
    • chrome requests favicon.ico even if there is no link in the html
    • should have deferred recoveries to catch panics in handlers