After amending an error using errors.WithMessage, printing the error with %+v prints the extra information after the stack trace instead of with the original message. For example:

package main

import (
	"log"

	"github.com/pkg/errors"
)

func a() error {
	return errors.New("error details")
}

func b() error {
	if err := a(); err != nil {
		return errors.WithMessage(err, "additional details")
	}
	return nil
}

func main() {
	if err := b(); err != nil {
		log.Fatalf("%+v", err)
	}
}

This prints:

2017/02/06 14:34:13 error details
main.a
	.../example.go:10
main.b
	.../example.go:14
main.main
	.../example.go:21
runtime.main
	/usr/local/Cellar/go/1.7.4_2/libexec/src/runtime/proc.go:183
runtime.goexit
	/usr/local/Cellar/go/1.7.4_2/libexec/src/runtime/asm_amd64.s:2086
additional details
exit status 1

As mentioned in #75, it seems like it would be more helpful to include the additional information with original error message. When using %v with the same example, it prints messages in this way now:

2017/02/06 14:33:32 additional details: error details
exit status 1