For the accounts maintained by geth, we don't need to worry about the transaction nonce because geth can add the correct nonce to the transactions and sign them. While using accounts that aren't managed by geth, we need to calculate the nonce ourselves.
To calculate the nonce ourselves, we can use the getTransactionCount method provided by geth. The first argument should be the address whose transaction count we need and the second argument is the block until we need the transaction count. We can provide the "pending" string as the block to include transactions from the block that's currently being mined. As we discussed in an earlier chapter, geth maintains a transaction pool in which it keeps pending and queued transactions. To mine a block, geth takes the pending transactions from the transaction pool and starts mining the new block. Until the block is not mined, the pending transactions remain in the transaction pool and once mined, the mined transactions...