Bug: blockchain.headers.subscribe and blockchain.scripthash.subscribe method not work

[eauxxs]

use electrum_client::{Client, ElectrumApi};

fn main() {
    let client = electrum_client::raw_client::RawClient::new(("blockstream.info", 143), None).unwrap();

    let r = client.block_headers_subscribe().unwrap();
    // print, but just once
    dbg!(r);  
    loop {
        std::thread::sleep(std::time::Duration::from_secs(5));
        let x = client.block_headers_pop().unwrap();
        // always is None
        dbg!(x);  
    }
}

client.block_headers_pop() is always None.

All clinet's jsonrpc calls use the self.call method. The self.call method constructs a request containing the id, and uses self.recv to wait for the result of the corresponding id. In self.recv, use self._reader_thread to wait for the result of this id, and then exit, ignoring the subsequent results of the subscription method.
Since this is a synchronous library, I looked for some trace of std::thead::spawn in the code, but couldn't find it.

1. Is my calling method wrong? This is a library that has been around for a long time. I think this is the reason. If yes, is it possible to add example code? This problem is really a headache.
2. When calling the subscription method, can a channel be returned instead of putting all the results into a VecDeque, which still requires the user to constantly check whether there is new data?