Timer config option

#60 + #61

implement the Unwrap() interface on unrecoverableError

unrecoverableError is possible to handle by errors.Is()
#59

call onRetry func if attempt is 0

#56

Infinite retry should have also delay

#55

fix: Context cancel add to errors

#53 #51

Infinity retry is possible

#49

resolve go module import path

#46

Exported default values are moved to the default function

#44

delay based on error

PR #35
issue #33

Add context support

PR #34
issue #33