io: call `tcp.set_nonblocking(true)` in `AsyncFd` example.
@@ -81,6 +81,7 @@ use std::{task::Context, task::Poll};
///
/// impl AsyncTcpStream {
/// pub fn new(tcp: TcpStream) -> io::Result<Self> {
+/// tcp.set_nonblocking(true)?;
/// Ok(Self {
/// inner: AsyncFd::new(tcp)?,
/// })
