multierror

multierror is a simple Go package for combining multiple errors. This is handy if you are concurrently running operations within a function that returns only a single error.

API

multierror exposes two types.

multierror.Errors is a []error with a receiver method Err(), which returns a multierror.MultiError instance or nil. You use this type to collect your errors by appending to it.

multierror.MultiError implements the error interface. Its Errors field contains the multierror.Errors you originally constructed.

Example

package main

import (
	"fmt"
	"github.com/joeshaw/multierror"
)

func main() {
	// Collect multiple errors together in multierror.Errors
	var e1 multierror.Errors
	e1 = append(e1, fmt.Errorf("Error 1"))
	e1 = append(e1, fmt.Errorf("Error 2"))

	// Get a multierror.MultiError from it
	err := e1.Err()

	// Output: "2 errors: Error 1; Error 2"
	fmt.Println(err)

	// Iterate over the individual errors
	merr := err.(*multierror.MultiError)
	for _, err := range merr.Errors {
		fmt.Println(err) // Output: "Error 1" and "Error 2"
	}

	// If multierror.Errors contains no errors, its Err() returns nil
	var e2 multierror.Errors
	err = e2.Err()

	// Output: "<nil>"
	fmt.Println(err)
}