How to Add Priority Fees to a Transaction

import {
  airdropFactory,
  appendTransactionMessageInstructions,
  createSolanaClient,
  createTransaction,
  generateKeyPairSigner,
  getComputeUnitEstimateForTransactionMessageFactory,
  getSignatureFromTransaction,
  lamports,
  pipe,
  prependTransactionMessageInstructions,
  setTransactionMessageFeePayerSigner,
  setTransactionMessageLifetimeUsingBlockhash,
  signTransactionMessageWithSigners
} from "gill";
import {
  getAddMemoInstruction,
  getSetComputeUnitLimitInstruction,
  getSetComputeUnitPriceInstruction
} from "gill/programs";

// Create an RPC
const { rpc, rpcSubscriptions, sendAndConfirmTransaction } = createSolanaClient(
  {
    urlOrMoniker: "localnet"
  }
);

// Create utility functions
const airdrop = airdropFactory({ rpc, rpcSubscriptions });
const getComputeUnitEstimate =
  getComputeUnitEstimateForTransactionMessageFactory({ rpc });

// Create and fund an account
const keypairSigner = await generateKeyPairSigner();

await airdrop({
  commitment: "confirmed",
  lamports: lamports(1000_000n),
  recipientAddress: keypairSigner.address
});

// Create a memo transaction
const { value: latestBlockhash } = await rpc.getLatestBlockhash().send();
const transactionMessage = createTransaction({
  feePayer: keypairSigner,
  version: "legacy",
  instructions: [
    getSetComputeUnitPriceInstruction({ microLamports: 5000n }),
    getAddMemoInstruction({ memo: "Hello, world!" })
  ],
  latestBlockhash
});

const estimatedComputeUnits = await getComputeUnitEstimate(transactionMessage);
console.log(
  `Transaction is estimated to consume ${estimatedComputeUnits} compute units`
);

// Add compute unit limit instruction to the transaction
const budgetedTransactionMessage = prependTransactionMessageInstructions(
  [getSetComputeUnitLimitInstruction({ units: estimatedComputeUnits })],
  transactionMessage
);

// Sign and send the transaction
const signedTx = await signTransactionMessageWithSigners(
  budgetedTransactionMessage
);
const transactionSignature = getSignatureFromTransaction(signedTx);
await sendAndConfirmTransaction(signedTx, { commitment: "confirmed" });
console.log(`Transaction Signature: ${transactionSignature}`);