Understanding async functions calls in Rust with RabbitMQ

I'm new in Rust and I am struggling a little bit with async functions. The goal of my program is to send messages to a RabbitMQ queue.

I have defined two functions, one to get the channel and another one to actually send the message:

//get the channel
async fn get_amqp_channel() -> Channel {
    let connection_arguments = OpenConnectionArguments::new(RABBIT_SERVER_URL, PORT, USER, PASSWORD);
    let connection = Connection::open(&connection_arguments).await.unwrap();
    return connection.open_channel(None).await.unwrap();
}

//send the message
async fn send_amqp_message(channel: &Channel, routing_key: &str, message: String) {
    let publish_arguments = BasicPublishArguments::new(EXCHANGE, routing_key);
    channel.basic_publish(BasicProperties::default(), message.into_bytes(), publish_arguments).await.unwrap();
}

If I call them from a async function like this, the message is never sent:

fn send_command() {
    //build message
    let rt = tokio::runtime::Runtime::new().unwrap();
    rt.block_on(send_message(message_type, serde_json::to_string(&message).unwrap()));
}

async fn send_message(message_type : String, message : String) {
    let channel = get_amqp_channel().await;
    send_amqp_message(&channel, get_routing_key(message_type).as_str(), message).await;
}

But, if I combine both functions into a single one, then everything works fine:

async fn send_message(message_type : String, message : String) {
    //get_amqp_channel
    let connection_arguments = OpenConnectionArguments::new(RABBIT_SERVER_URL, PORT, USER, PASSWORD);
    let connection = Connection::open(&connection_arguments).await.unwrap();
    let channel = connection.open_channel(None).await.unwrap();
    
    //send_amqp_message
    let publish_arguments = BasicPublishArguments::new(EXCHANGE, get_routing_key(message_type).as_str());
    channel.basic_publish(BasicProperties::default(), message.into_bytes(), publish_arguments).await.unwrap();
}

As far as I understand, it shouldn't be any difference, since the block_on call forces the whole program to wait for the future to end. Where is my mistake?

Any help would be welcome.

Thank you very much.

Finally, I have found the problem: in the get_amqp_channel function, a Channel struct is returned, which has a Connection element inside. When the control returns to the main function, the connection is not longer active, so when the time for sending the message comes, there's no connection linked to this channel (channel.is_connection_open() == false).

It seems to me that connection is automatically closed whenever the connection variable is out of scope.