/// Node of ROS2.
pub struct Node {
    node: rcl::rcl_node_t,
    name: String,
    namespace: Option<String>,
    init_param_server: InitOnce,
    pub(crate) context: Arc<Context>,
}

let logger = Logger::new("async task");
let mut subscriber1 = node.create_subscriber::<std_msgs::msg::String>("topic1", None)?;
let mut subscriber2 = node.create_subscriber::<std_msgs::msg::String>("topic2", None)?;
loop {
         let msg1 = subscriber1.recv().await?;
         let msg2 = subscriber2.recv().await?;
         pr_info!(logger, "{}", msg1.data);
         pr_info!(logger, "{}", msg2.data);
}

#[repr(C)]
#[derive(Debug)]
pub struct DiagnosticArray {
    pub header: std_msgs::msg::Header,
    pub status: DiagnosticStatusSeq<0>,
}

let mut diagnostics = DiagnosticArray::new().unwrap();
let status = DiagnosticStatusSeq::<5>::new(4).unwrap();
unsafe { diagnostics.status = std::mem::transmute(status)};

impl<const N: usize> DiagnosticArraySeq<N> {
    /// Create a sequence of.
    /// `N` represents the maximum number of elements.
    /// If `N` is `0`, the sequence is unlimited.
    pub fn new(size: usize) -> Option<Self> {
        if N != 0 && size >= N {
            // the size exceeds in the maximum number
            return None;
        }

tokio::select! {
       _ = tokio::signal::ctrl_c() => {},                                                                                                                                                                               
       _ = task1 => {},                                                                                                                                                                                                 
};