Sign transaction outside of CreateRawTransaction about solana-go-sdk HOT 3 CLOSED

package main

import (
	"context"
	"crypto/ed25519"
	"fmt"

	"github.com/portto/solana-go-sdk/client"
	"github.com/portto/solana-go-sdk/client/rpc"
	"github.com/portto/solana-go-sdk/common"
	"github.com/portto/solana-go-sdk/types"
)

func main() {
	// connection
	c := client.NewClient(rpc.DevnetRPCEndpoint)

	// fee payer
	feePayer := types.AccountFromPrivateKeyBytes([]byte{})

	// compose message
	message := types.NewMessage(
		feePayer.PublicKey,
		[]types.Instruction{},
		"RECNET BLOCK HASH HERE",
	)

	// serialize message for signing
	serilizedMessage, err := message.Serialize()
	if err != nil {
		// handle error here
	}

	// create tx with signatures
	tx, err := types.CreateTransaction(
		message,
		map[common.PublicKey]types.Signature{
			feePayer.PublicKey: ed25519.Sign(feePayer.PrivateKey, serilizedMessage),
			// other pubkey: other sig
		})
	if err != nil {
		// handle error here
	}

	// serialize tx
	rawTx, err := tx.Serialize()
	if err != nil {
		// handle error here
	}

	// send it
	sig, err := c.SendRawTransaction(context.Background(), rawTx)
	if err != nil {
		// handle error here
	}
	fmt.Println(sig)
}

package main

import (
	"context"
	"fmt"

	"github.com/portto/solana-go-sdk/client"
	"github.com/portto/solana-go-sdk/client/rpc"
	"github.com/portto/solana-go-sdk/common"
	"github.com/portto/solana-go-sdk/program/sysprog"
	"github.com/portto/solana-go-sdk/types"
)

var feePayer = types.AccountFromPrivateKeyBytes()

func main() {
	// connection
	c := client.NewClient(rpc.DevnetRPCEndpoint)

	a := types.NewAccount()

	message := types.NewMessage(
		feePayer.PublicKey,
		[]types.Instruction{
			sysprog.CreateAccount(
				feePayer.PublicKey,
				a.PublicKey,
				common.SystemProgramID,
				1e9,
				1,
			),
		},
		"RECENT BLOCK HASH HERE",
	)
	rawMessage, err := message.Serialize()
	if err != nil {
		// handle error
	}

	// you can pass signer here 
	tx, err := types.NewTransaction(message, []types.Account{feePayer})
	if err != nil {
		// handle error
	}

	// or add signature later!
	tx.AddSignature(a.Sign(rawMessage))

	sig, err := c.SendTransaction2(context.Background(), tx)
	if err != nil {
		// handle error
	}
	fmt.Println(sig)
}