It's not a bug, just I think the second judgment condition is not necessary.

[yudidi]

In branch part_5, blockchain.go#L109:

blockchain_go/blockchain.go

Line 109 in 201e7a1

if out.IsLockedWithKey(pubKeyHash) && accumulated < amount {

The second judgment condition accumulated < amount is not necessary. It only works when amount <= 0, In this case, we should check the value of amount at the beginning of the function.

func (bc *Blockchain) FindSpendableOutputs(pubKeyHash []byte, amount int) (int, map[string][]int) {
	unspentOutputs := make(map[string][]int)
	accumulated := 0
        // Maybe we should check “amount” at the beginning of the function.
	if (amount <= 0){ 
		return accumulated,unspentOutputs
	}
	unspentTXs := bc.FindUnspentTransactions(pubKeyHash)
	
Work:
	for _, tx := range unspentTXs {
		txID := hex.EncodeToString(tx.ID)

		for outIdx, out := range tx.Vout {
			if out.IsLockedWithKey(pubKeyHash)  { // Delete “&& accumulated < amount”
				accumulated += out.Value
				unspentOutputs[txID] = append(unspentOutputs[txID], outIdx)

				if accumulated >= amount {
					break Work 
				}
			}
		}
	}
	return accumulated, unspentOutputs
}