Rust

use std::hint::unreachable_unchecked;
use std::io::{stdin, stdout, Read, Write};
pub fn main() {
    let key = b"draw!";
    let temp = stdin();
    let mut stdin = temp.lock();
    let tmp = stdout();
    let mut out = tmp.lock();
    let mut i = 0;
    let mut buf = [0];
    loop {
        stdin
            .read(&mut buf)
            .unwrap_or_else(|_| unsafe { unreachable_unchecked() });
        let read = *unsafe { buf.get_unchecked(0) };
        if unsafe { read == *key.get_unchecked(i) } {
            i += 1;
        } else {
            i = (read == b'd') as usize;
        }
        if i == 5 {
            out.write(b"bang!")
                .unwrap_or_else(|_| unsafe { unreachable_unchecked() });
            out.flush()
                .unwrap_or_else(|_| unsafe { unreachable_unchecked() });
            break;
        }
    }
}

Try it online!

A solution in rust. It is pretty similar to @hyper-neutrino's solution, but it makes sure to flush the output buffer after writing and also asserts that io errors can't happen (it will be undefined behavior if they do, probably causing a sigill). Build rustc -Copt-level=3 -Clto=fat -Ctarget-cpu=native -o main and run ./main