Remove netcat dependency from example

[kazuk]

Motivation

We want to dockernize

#221

I try to build docker build and run.

$ docker run b230c49234ba
waiting JSON records in tcp/54300 port...
[2022-07-09T22:39:44Z ERROR panic] thread 'main' panicked at 'send failed: Os { code: 2, kind: NotFound, message: "No such file or directory" }': springql/examples/doc_app1.rs:23

crashed at this function.

fn send_data_to_pipeline() {
    Command::new("bash")
        .arg("-c")
        .arg(r#"echo '{"ts": "2022-01-01 13:00:00.000000000", "temperature": 5.3}' |nc localhost 54300"#)
        .spawn()
        .expect("send failed");
}

Refactoring target

Do not use to netcat.

[laysakura]

@kazuk I added an example that uses in-memory queue for both source and sink.
https://github.com/SpringQL/SpringQL/blob/main/springql/examples/in_memory.rs

How about using this for #221 ?
Note that this example runs forever so you may want to make a slight fix to it.