// Solana Memo Program 
val account = SolanaPublicKey(keyPair.publicKey)
val memoProgramId = SolanaPublicKey.from("MemoSq4gqABAXKb96qnH8TysNcWxMyWCqXgDLGmfcHr")
val memoInstruction = TransactionInstruction(
    memoProgramId,
    listOf(AccountMeta(account, true, true)),
    "hello world ".encodeToByteArray()
)

// Build Message
val blockhash = Blockhash(getRecentBlockhash())
val message = Message.Builder()
    .addInstruction(memoInstruction)
    .setRecentBlockhash(blockhash)
    .build()

// prepare signer
val keyPair = Ed25519.generateKeyPair()
val signer = object : Ed25519Signer() {
    override val publicKey: ByteArray get() = keyPair.publicKey
    override suspend fun signPayload(payload: ByteArray): ByteArray = Ed25519.sign(keyPair, payload)
}

// Sign Message
val signature = signer.signPayload(message.serialize())

// Build Transaction
val transaction = Transaction(listOf(signature), message)

// serialize transaction
val transactionBytes = transaction.serialize()
val encodedTransaction = Base58.encodeToString(transactionBytes)

// setup RPC driver
val rpcUrl = "https://api.endpoint.com"
val rpcDriver = Rpc20Driver(rpcUrl, MyNetworkDriver())

class SendTransactionRequest(encodedTransaction: String, requestId: String)
    : JsonRpc20Request(
        method = "sendTransaction",
        params = buildJsonArray {
            add(encodedTransaction)
        },
        requestId
    )

// build rpc request
val requestId = 1
val rpcRequest = SendTransactionRequest(encodedTransaction, requestId)

// send the request and get response
// using JsonElement.serializer() will return the JSON RPC response. you can use your own serializer to get back a specific object
val rpcResponse = rpcDriver.makeRequest(rpcRequest, JsonElement.serializer())