MongoDB Like Unique ID Generator

generator.go

package main

import (
	"crypto/rand"
	"encoding/binary"
	"fmt"
	"time"
)

type ObjectId [12]byte

var (
	processUniqueValue = make([]byte, 5)
	counter            = initCounter()
)

func init() {
	// Generate a random 5-byte value for the process
	if _, err := rand.Read(processUniqueValue); err != nil {
		panic(err)
	}
}

func initCounter() []byte {
	// Generate a random 3-byte value for the counter
	counter := make([]byte, 3)
	if _, err := rand.Read(counter); err != nil {
		panic(err)
	}
	return counter
}

func NewObjectId() ObjectId {
	// Timestamp in seconds since the Unix epoch
	timestamp := time.Now().Unix()

	var id ObjectId

	// Add 4-byte timestamp to the ObjectId
	binary.BigEndian.PutUint32(id[0:4], uint32(timestamp))

	// Add 5-byte processUniqueValue to the ObjectId
	copy(id[4:9], processUniqueValue)

	// Add 3-byte counter to the ObjectId
	copy(id[9:], counter)
	incrementCounter()

	return id
}

func (id ObjectId) ToString() string {
	return fmt.Sprintf("%x", id)
}

func incrementCounter() {
	for i := 2; i >= 0; i-- {
		counter[i]++
		if counter[i] != 0 {
			break
		}
	}
}