gistfile1.txt

use std::io;
use std::io::Read;
use std::fs::File;
use std::error::Error;
fn main() -> Result<(), Box<dyn Error>> {
    read_username_from_file()?;
    Ok(())
}
fn read_username_from_file() -> Result<String, io::Error> {
    let mut s = String::new();
    File::open("hello.txt")?.read_to_string(&mut s)?;
    Ok(s)
}