Simple blockchain example

main.go

package main

import (
	"crypto/sha256"
	"encoding/hex"
	"strconv"
	"time"
)

type Data struct {
	Transaction string
}

func (data *Data) string() string {
	return data.Transaction
}

type Block struct {
	Index          int
	Timestamp      time.Time
	Data           Data
	PrevHash, Hash string
}

func (block *Block) string() string {
	return strconv.Itoa(block.Index) + block.Timestamp.String() + block.Data.string() + block.PrevHash
}
func (block *Block) computeHash() string {
	hash := sha256.New()
	hash.Write([]byte(block.string()))
	return hex.EncodeToString(hash.Sum(nil))
}

type Blockchain struct {
	blocks []Block
}

func (blockchain *Blockchain) addBlock(data Data) int {
	var block Block
	block.Index = len(blockchain.blocks)
	block.Timestamp = time.Now()
	block.Data = data
	if block.Index > 0 {
		block.PrevHash = blockchain.blocks[block.Index-1].Hash
	}
	block.Hash = block.computeHash()
	blockchain.blocks = append(blockchain.blocks, block)
	return block.Index
}

func (blockchain *Blockchain) validateHash() bool {
	for i := 1; i < len(blockchain.blocks); i++ {
		if blockchain.blocks[i].PrevHash != blockchain.blocks[i-1].Hash {
			return false
		}
	}
	return true
}

func main() {
	var blockchain Blockchain
	blockchain.addBlock(Data{"foo"})
	blockchain.addBlock(Data{"bar"})
	blockchain.addBlock(Data{"baz"})
	for _, block := range blockchain.blocks {
		println(block.Hash, block.PrevHash)
	}
	println(blockchain.validateHash())
}