为什么即使我有＃[tokio :: main]，也会收到错误消息“没有反应堆在运行，必须从Tokio运行时的上下文中调用”？

我正在跟踪mdns Rust文档并粘贴了示例代码，但它引发以下错误：

thread 'main' panicked at 'there is no reactor running, must be called from the context of Tokio runtime'

这是我的代码：

use futures_util::{pin_mut, stream::StreamExt};
use mdns::{Error, Record, RecordKind};
use std::{net::IpAddr, time::Duration};

const SERVICE_NAME: &'static str = "_googlecast._tcp.local";

#[tokio::main]
async fn main() -> Result<(), Error> {
    // Iterate through responses from each Cast device, asking for new devices every 15s
    let stream = mdns::discover::all(SERVICE_NAME, Duration::from_secs(15))?.listen();
    pin_mut!(stream);

    while let Some(Ok(response)) = stream.next().await {
        let addr = response.records().filter_map(self::to_ip_addr).next();

        if let Some(addr) = addr {
            println!("found cast device at {}", addr);
        } else {
            println!("cast device does not advertise address");
        }
    }

    Ok(())
}

fn to_ip_addr(record: &Record) -> Option<IpAddr> {
    match record.kind {
        RecordKind::A(addr) => Some(addr.into()),
        RecordKind::AAAA(addr) => Some(addr.into()),
        _ => None,
    }
}

依存关系：

[dependencies]
mdns = "1.1.0"
futures-util = "0.3.8"
tokio = { version = "0.3.3", features = ["full"] }

我想念什么？我尝试在网上查找，但没有找到如何为该用例创建反应堆。