feat(transaction-builder): Add support for extensible async signer

bindings/go/examples/gas_station/main.go

@@ -5,8 +5,9 @@ package main
 
 import (
 	"fmt"
-	"github.com/iotaledger/iota-rust-sdk/bindings/go/iota_sdk"
 	"log"
+
+	"github.com/iotaledger/iota-rust-sdk/bindings/go/iota_sdk"
 )
 
 func identifier(ident string) *iota_sdk.Identifier {
@@ -23,7 +24,7 @@ func main() {
 	gasStationAuthToken := "test"
 	keypair := iota_sdk.Ed25519PrivateKeyGenerate()
 	sender := keypair.PublicKey().DeriveAddress()
-	simpleKey := iota_sdk.SimpleKeypairFromEd25519(keypair)
+	signer := iota_sdk.TransactionSignerFromEd25519(keypair)
 
 	builder := iota_sdk.NewTransactionBuilder(sender).WithClient(client)
 
@@ -45,7 +46,7 @@ func main() {
 
 	builder.GasStationSponsor(gasStationUrl, nil, &headers)
 
-	res, err := builder.Execute(simpleKey, nil)
+	res, err := builder.Execute(signer, nil)
 	if err.(*iota_sdk.SdkFfiError) != nil {
 		log.Fatalf("Failed to sponsor transaction: %v", err)
 	}

bindings/go/examples/transaction_signer_callback/main.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2025 IOTA Stiftung
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"log"
+
+	"github.com/iotaledger/iota-rust-sdk/bindings/go/iota_sdk"
+)
+
+type AsyncSigner struct {
+	Key *iota_sdk.Ed25519PrivateKey
+}
+
+func (signer *AsyncSigner) Sign(transaction *iota_sdk.Transaction) (iota_sdk.TransactionSignerFnOutput, error) {
+	signature, err := signer.Key.SignTransaction(transaction)
+	return iota_sdk.TransactionSignerFnOutput{Signature: signature}, err
+}
+
+func main() {
+	recipientAddress, err := iota_sdk.AddressFromHex("0x0000a4984bd495d4346fa208ddff4f5d5e5ad48c21dec631ddebc99809f16900")
+	if err != nil {
+		log.Fatalf("Failed to parse recipient address: %v", err)
+	}
+
+	privateKey, err := iota_sdk.NewEd25519PrivateKey(make([]byte, 32))
+	if err != nil {
+		log.Fatalf("Failed to create private key: %v", err)
+	}
+	publicKey := privateKey.PublicKey()
+	senderAddress := publicKey.DeriveAddress()
+	log.Printf("Sender address: %s", senderAddress.ToHex())
+
+	// Request funds from faucet
+	faucet := iota_sdk.FaucetClientNewLocalnet()
+	_, err = faucet.RequestAndWait(senderAddress)
+	if err.(*iota_sdk.SdkFfiError) != nil {
+		log.Fatalf("Failed to request faucet: %v", err)
+	}
+
+	client := iota_sdk.GraphQlClientNewLocalnet()
+
+	builder := iota_sdk.NewTransactionBuilder(senderAddress).WithClient(client)
+	builder.SendIota(recipientAddress, iota_sdk.PtbArgumentU64(1000))
+
+	signer := iota_sdk.NewTransactionSigner(&AsyncSigner{Key: privateKey})
+	waitFor := iota_sdk.WaitForTxFinalized
+	effects, err := builder.Execute(signer, &waitFor)
+	if err.(*iota_sdk.SdkFfiError) != nil {
+		log.Fatalf("Failed to execute: %v", err)
+	}
+	log.Printf("Digest: %s", iota_sdk.HexEncode((*effects).Digest().ToBytes()))
+	log.Printf("Transaction status: %v", (*effects).AsV1().Status)
+	log.Printf("Effects: %+v", (*effects).AsV1())
+}