spanner: fix function signature in doc
@@ -278,7 +278,7 @@ You pass in a function to ReadWriteTransaction, and the client will handle the
retries automatically. Use the transaction's BufferWrite method to buffer
mutations, which will all be executed at the end of the transaction:
- _, err := client.ReadWriteTransaction(ctx, func(txn *spanner.ReadWriteTransaction) error {
+ _, err := client.ReadWriteTransaction(ctx, func(ctx context.Context, txn *spanner.ReadWriteTransaction) error {
var balance int64
row, err := txn.ReadRow(ctx, "Accounts", spanner.Key{"alice"}, []string{"balance"})
if err != nil {
