我在db.txt中存放了如下user name数据： alice bob david

下面的函数是从标准输入读取user name, 然后与存放在db.txt中的数据对比，如果存在，则打印exist，如果不存在，则写入到db.txt. 但是下面的函数check_user_exist中，match第一个条件总是匹配的，这是为什么呢？

use std::fs::File;
use std::io::{self, prelude::*, BufReader};
use std::path::Path;
use std::fs::OpenOptions;
use std::io::Write;

pub fn login()->io::Result<()>{
    db_init();

    let mut name = String::new();
    io::stdin().read_line(&mut name)?;
    match check_user_exist(name.as_str()) {
        Ok(exist) => println!("{:?}",exist),
        Err(_) => println!("register new name."),
    }
    Ok(())
}

fn check_user_exist(name:&str) -> io::Result<()> {

    let file = File::open("db.txt")?;
    let reader = BufReader::new(file);
    for line in reader.lines().map(|l| l.unwrap()) {
        match line.as_str(){
            name  => println!("found str {}",name),   // **always match, why ?? **
            _ => register(name),
        }
    }
    Ok(())
}  

fn register(name:&str){

    let mut file = OpenOptions::new().append(true).open("db.txt").expect(
        "cannot open file");
     file.write_all(name.as_bytes()).expect("write file faile");
}

fn db_init(){
    if Path::new("db.txt").exists() {
        println!("db already inited!");
    }
    else{
        println!("db not initialized. create db file!");
        let file = File::create("db.txt").expect("create file fail");
    }
}

fn main(){
    println!("start main\n");

    login();
}