Stringer() vs GoStringer()

stringer.go

package main

import "fmt"

type AccessCheckStatus int

const (
	_ AccessCheckStatus = iota
	// Allow ...
	Allow
	// Deny ...
	Deny
	// DenyNotMatched ...
	DenyNotMatched
	// DenyByPolicy ...
	DenyByPolicy
	// DenyRoleNotFound ...
	DenyRoleNotFound
	// DenyDomainNotMatched ...
	DenyDomainNotMatched
	// DenyInvalidSignature ...
	DenyInvalidSignature
	// DenySignatureNotFound ...
	DenySignatureNotFound
	// DenyInvalidExpire ...
	DenyInvalidExpire
	// DenyExpired ...
	DenyExpired
)

// activate the following comment-outed code
// to see %#v prints string.
// func (ac AccessCheckStatus) GoString() string {
// 	return ac.String()
// }

func (ac AccessCheckStatus) String() string {
	switch ac {
	case Allow:
		return "Allow"
	case Deny:
		return "Deny"
	case DenyNotMatched:
		return "DenyNotMatched"
	case DenyByPolicy:
		return "DenyByPolicy"
	case DenyRoleNotFound:
		return "DenyRoleNotFound"
	case DenyDomainNotMatched:
		return "DenyDomainNotMatched"
	case DenyInvalidSignature:
		return "DenyInvalidSignature"
	case DenySignatureNotFound:
		return "DenySignatureNotFound"
	case DenyInvalidExpire:
		return "DenyInvalidExpire"
	case DenyExpired:
		return "DenyExpired"
	default:
		return "Unknown"
	}
}

func main() {
	hoge(Allow)
}

// https://golang.org/pkg/fmt/#GoStringer
func hoge(value interface{}) {
	fmt.Println("entering hoge")

	// %v the value in a default format
	// when printing structs, the plus flag (%+v) adds field names
	fmt.Printf("%%v: %v\n", value)

	// %#v a Go-syntax representation of the value
	fmt.Printf("%%#v: %#v\n", value)

	// %T a Go-syntax representation of the type of the value
	fmt.Printf("%%T: %T\n", value)
	fmt.Println("leaving hoge")
}