Where to put the type info?

main.rs

use std::thread;
use tokio::runtime::Runtime;
use tokio_modbus::prelude::*;
use tokio_serial::Serial;

fn main() {
    thread::spawn(|| {
        let mut rt = Runtime::new().expect("Couldn't create Runtime");
        rt.block_on(async {
            let port = Serial::from_path("/dev/ttyUSB0", &Default::default()).unwrap();
            let mut ctx = rtu::connect_slave(port, 247.into()).await?;
            let data = ctx.read_input_registers(0, 10).await?;
            println!("{:?}", data);
            Ok(())
        })
    })
    .join()
    .unwrap();
}

This returns an error like this:

error[E0282]: type annotations needed
  --> src/main.rs:11:27
   |
9  |         rt.block_on(async {
   |            -------- help: consider specifying the type argument in the method call: `block_on::<F>`
10 |             let port = Serial::from_path("/dev/ttyUSB0", &Default::default()).unwrap();
11 |             let mut ctx = rtu::connect_slave(port, 247.into()).await?;
   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type