If an unrecoverable error is encountered before the final attempt, the length of the error returned by Do is equal to the maximum number of attempts rather than the actual number. This behaviour is demonstrated by the following program.

package main

import (
	"errors"
	"fmt"

	"github.com/avast/retry-go/v4"
)

func main() {
	i := 0

	err := retry.Do(
		func() error {
			err := fmt.Errorf("error %d", i)

			if i > 1 {
				err = retry.Unrecoverable(err)
			}

			i++
			return err
		},
	)

	fmt.Println(err)

	var e retry.Error
	if errors.As(err, &e) {
		fmt.Println(len(e))
	}
}

The following output is observed when using v4.3.1.

All attempts fail:
#1: error 0
#2: error 1
#3: error 2
10

The following output is expected instead, where the length of the slice is equal to the number of attempts.

All attempts fail:
#1: error 0
#2: error 1
#3: error 2
3