我想用Rust创建一个REST API，但无法让它正常工作。
到目前为止，我的相关代码如下：
在 main.rs 中：
#[actix_web::main]
async fn main() -> std::io::Result<()> {
    // 将 .env 加载到环境变量中。
    dotenv::dotenv().ok();
    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
    // 设置数据库连接池
    let database_url = std::env::var("DATABASE_URL").expect("DATABASE_URL");
    let manager = ConnectionManager::<PgConnection>::new(database_url);
    let pool: DbPool = r2d2::Pool::builder()
        .test_on_check_out(true)
        .build(manager)
        .expect("Could not build connection pool");
    let port = std::env::var("PORT").expect("$PORT is not set.");
    HttpServer::new(move || {
        App::new()
            .app_data(web::Data::new(pool.clone()))
            .wrap(middleware::Logger::default())
            .route("/", web::get().to(|| async { "Actix REST API" }))
            .service(handlers::common::houses::index)
    })
    .bind(("0.0.0.0", port.parse().unwrap()))?
    .run()
    .await
}
模式：
diesel::table! {
  houses (id) {
    id -> Int4,
    user_id -> Varchar,
    street -> Varchar,
    figure -> Varchar,
    floor -> Varchar,
    create_date -> Timestamp,
    update_date -> Timestamp,
    is_deleted -> Bool,
  }
}
模型：
#[derive(Debug, Serialize, Deserialize, Queryable)]
pub struct House {
    pub id: i32,
    pub user_id: String,
    pub street: String,
    pub figure: String,
    pub floor: String,
    pub create_date: chrono::NaiveDateTime,
    pub update_date: chrono::NaiveDateTime,
    pub is_deleted: bool,
}
处理程序：
#[get("/houses")]
async fn index(pool: web::Data<DbPool>) -> Result<HttpResponse, Error> {
    let houses = web::block(move || {
        let conn = &pool.get()?;
        find_all(&conn)
    })
    .await?
    .map_err(actix_web::error::ErrorInternalServerError)?;
    Ok(HttpResponse::Ok().json(houses))
}
fn find_all(conn: &PgConnection) -> Result<Vec<House>, DbError> {
    use crate::schemas::common::houses::houses::dsl::*;
    let items = houses.load::<House>(&mut conn)?;
    Ok(items)
}
依赖项为：
[dependencies]
actix-web = "4"
chrono = { version = "0.4.19", features = ["serde"] }
diesel = { version = "2.0.3", features = ["postgres", "r2d2", "chrono"] }
dotenv = "0.15.0"
env_logger = "0.10.0"
serde = { version = "1.0.136", features = ["derive"] }
serde_json = "1.0"
它一直报错，我不明白原因。
错误信息为：
error[E0277]: the trait bound `&diesel::PgConnection: LoadConnection` is not satisfied
src\handlers\common\houses.rs:25:37
| 25 | let items = houses.load::<House>(&mut conn)?;
| ---- | -^^^^^^^^
| | | the trait `LoadConnection` is not implemented for `&diesel::PgConnection`
help: consider removing the leading `&`-reference required by a bound introduced by this call
| note: required for `table` to implement `LoadQuery<'_, &diesel::PgConnection, House>`
note: required by a bound in `diesel::RunQueryDsl::load`
我在 diesel 版本 1.4 中见过类似的错误，但我认为这个版本不同。
另外，我刚开始使用 Rust，目前有点迷茫。
我希望有人知道问题所在以及如何解决它。

`PgConnection` 实现了 [`LoadConnection`](https://docs.rs/diesel/2.0.3/diesel/connection/trait.LoadConnection.html)，但 `&PgConnection` 不是（注意多余的 `&`）。
将 `conn` 变为可变引用并传递：
```rust
#[get("/houses")]
async fn index(pool: web::Data<DbPool>) -> Result<HttpResponse, Error> {
    let houses = web::block(move || {
        let mut conn = pool.get()?; // <------------
        find_all(&mut conn)         // <------------
    })
    .await?
    .map_err(actix_web::error::ErrorInternalServerError)?;
    Ok(HttpResponse::Ok().json(houses))
}
fn find_all(conn: &mut PgConnection) -> Result<Vec<House>, DbError> {
                // ^^^ <------------
    use crate::schemas::common::houses::houses::dsl::*;
    let items = houses.load::<House>(conn)?; // <------------
    Ok(items)
}