How to use a proxy with Rust reqwest

[dependencies]reqwest = { version = "0.13", features = ["socks"] }tokio = { version = "1", features = ["full"] }

use std::time::Duration;use reqwest::{Client, Proxy};fn arc_client(username: &str) -> reqwest::Result<Client> {    Client::builder()        .proxy(Proxy::all("http://proxy.arcproxies.io:8000")?.basic_auth(username, "PASSWORD"))        .connect_timeout(Duration::from_secs(10))        .timeout(Duration::from_secs(30))        .build()}#[tokio::main]async fn main() -> Result<(), Box<dyn std::error::Error>> {    let client = arc_client("USERNAME_pool-arcfast_country-de")?;    let body = client.get("https://api.ipify.org?format=json").send().await?.text().await?;    println!("{body}");    Ok(())}

use std::time::{SystemTime, UNIX_EPOCH};fn new_handle() -> String {    // any unique string works; use the rand crate in real code    let n = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().subsec_nanos();    format!("{n:08x}")}async fn crawl_listing(start: &str) -> Result<(), reqwest::Error> {    let user = format!("USERNAME_pool-arcfast_country-de_session-{}_sesstime-10", new_handle());    let session = arc_client(&user)?;    for page in 1..=3 {        let res = session.get(format!("{start}?page={page}")).send().await?;        println!("{page} {}", res.status());    }    Ok(())}

let markets = [    ("de-cologne", "USERNAME_pool-arcfast_country-de_city-cologne"),    ("us-dallas",  "USERNAME_pool-arcfast_country-us_city-dallas"),    ("jp-tokyo",   "USERNAME_pool-arcfast_country-jp_city-tokyo"),];for (market, user) in markets {    let res = arc_client(user)?.get("https://example.com/price/123").send().await?;    println!("{market} {}", res.status());}

use std::error::Error as _;use reqwest::StatusCode;fn is_proxy_auth_error(err: &reqwest::Error) -> bool {    let mut source = err.source();    while let Some(e) = source {        if e.to_string().contains("proxy authorization required") {            return true;        }        source = e.source();    }    false}async fn fetch(url: &str) -> Result<String, Box<dyn std::error::Error>> {    for attempt in 0..4u32 {        let user = format!("USERNAME_pool-arcfast_country-de_session-{}_sesstime-5", new_handle());        match arc_client(&user)?.get(url).send().await {            Ok(res) if res.status() == StatusCode::PROXY_AUTHENTICATION_REQUIRED => {                return Err("proxy rejected the credentials".into())            }            Ok(res) if res.status() != StatusCode::TOO_MANY_REQUESTS && !res.status().is_server_error() => {                return Ok(res.text().await?)            }            Err(e) if is_proxy_auth_error(&e) => return Err("proxy rejected the credentials".into()),            _ => {} // timeout, connection error, 429 or 5xx: retry        }        tokio::time::sleep(std::time::Duration::from_secs(1 << attempt)).await;    }    Err(format!("gave up on {url}").into())}