How I write microservice (part 2)

id.go

package helpers

import (
	"github.com/dchest/uniuri"
	validation "github.com/go-ozzo/ozzo-validation"
	"github.com/go-ozzo/ozzo-validation/is"
)

// IDGeneratedLength defines the length of the id string
const IDGeneratedLength = 32

// IDGeneratorFunc returns a randomly generated string useable as identifier
var IDGeneratorFunc = func() string {
	return uniuri.NewLen(IDGeneratedLength)
}

// IDValidationRules describes identifier contract for syntaxic validation
var IDValidationRules = []validation.Rule{
	validation.Required,
	validation.Length(IDGeneratedLength, IDGeneratedLength),
	is.Alphanumeric,
}

principal.go

package helpers

import (
	"encoding/base64"

	"golang.org/x/crypto/blake2b"
)

var principalHashKey = []byte(`7EcP%Sm5=Wgoce5Sb"%[E.<&xG8t5soYU$CzdIMTgK@^4i(Zo|)LoDB'!g"R2]8$`)

// PrincipalHashFunc return the principal hashed using Blake2b keyed algorithm
var PrincipalHashFunc = func(principal string) string {
	// Prepare hasher
	hasher, err:= blake2b.New512(principalHashKey)
	if err!= nil {
		panic(err)
	}

	// Append principal
	_, err = hasher.Write([]byte(principal))
	if err!= nil {
		panic(err)
	}

	// Return base64 hash value of the principal hash
	return base64.RawStdEncoding.EncodeToString(hasher.Sum(nil))
}

// SetPrincipalHashKey used to set the key of hash function
func SetPrincipalHashKey(key []byte) {
	if len(key)!= 64 {
		panic("Principal hash key length must be 64bytes long.")
	}

	principalHashKey = key
}