Compose multiple errors into one

errors.go

package main

import "fmt"

// Errors allows you to compose multiple errors
type Errors []error

func (e Errors) Error() string {
	if len(e) == 1 {
		return e[0].Error()
	}

	msg := "multiple errors:"
	for i, err := range e {
		msg = fmt.Sprintf("%s\n\t%2d: %s", msg, i, err.Error())
	}
	return msg
}