actix-web: The trait bound `Ws: actix::actor::Actor` is not satisfied

Problem: The trait bound `Ws: actix::actor::Actor` is not satisfied compile error.

Your Environment:

$ uname -a
Linux dev 5.4.0-70-generic #78~18.04.1-Ubuntu SMP Sat Mar 20 14:10:07 UTC 2021 x86_64 x86_64 x86_64 GNU/Linu

Rust Version (I.e, output of rustc -V):

$ rustc -V
rustc 1.51.0 (2fd73fabe 2021-03-23)

Actix Web Version:

[dependencies]
actix = "0.11.0"
actix-web = "3"
actix-web-actors = "3.0.0"

Test Code:

use actix::prelude::*;
use actix_web_actors::*;

struct Ws;

impl Actor for Ws {
    type Context = ws::WebsocketContext<Self>;
}


impl StreamHandler<Result<ws::Message, ws::ProtocolError>> for Ws {
    fn handle(&mut self, msg: Result<ws::Message, ws::ProtocolError>, ctx: &mut Self::Context) {
        match msg.unwrap() {
            ws::Message::Ping(msg) => ctx.pong(&msg),
            ws::Message::Text(text) => ctx.text(text),
            ws::Message::Binary(bin) => ctx.binary(bin),
            ws::Message::Close(reason) => ctx.close(reason),
            _ => {}
        }
    }
}

fn main() {
    println!("Hello, world!");
}

Error:

error[E0277]: the trait bound `Ws: actix::actor::Actor` is not satisfied
   --> src/main.rs:7:5
    |
7   |     type Context = ws::WebsocketContext<Self>;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `actix::actor::Actor` is not implemented for `Ws`