如何在vapor中使用PostgreSQL事务

import Vapor
import FluentPostgreSQL

public func configure(_ config: inout Config, _ env: inout Environment, _ services: inout Services) throws {
    // ...
    
    try services.register(FluentPostgreSQLProvider())
    
    let postgresqlConfig = PostgreSQLDatabaseConfig(hostname: "localhost", port: 5432, username: "your_username", database: "your_database", password: "your_password")
    services.register(postgresqlConfig)
    
    // ...
}

final class Todo: PostgreSQLModel {
    var id: Int?
    var title: String
    
    init(id: Int? = nil, title: String) {
        self.id = id
        self.title = title
    }
}

extension Todo: Migration { }

extension Todo: Content { }

router.post("todos") { req -> Future<Todo> in
    return req.withPooledConnection(to: .psql) { conn in
        return conn.transaction(on: .psql) { conn in
            let todo = Todo(title: "New Todo")
            return todo.save(on: conn).map { _ in
                return todo
            }
        }
    }
}