sentinel errors

#Go

io.EOF のように例外を表すというより制御フローを導くシグナルとしてのエラーの分類

https://dave.cheney.net/2016/04/27/dont-just-check-errors-handle-them-gracefully

>The name descends from the practice in computer programming of using a specific value to signify that no further processing is possible. So to with Go, we use specific values to signify an error.

> Examples include values like io.EOF or low level errors like the constants in the syscall package, like syscall.ENOENT.