Code shared from the Rust Playground

playground.rs

use serde::Serialize;

#[derive(Serialize)]
enum Token {
    S(String),
    _I(i32),
}

#[derive(Serialize)]
struct Foo {
    r#type: String,
    token: Token,
    challenge: String,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let params = Foo {
        token: Token::S("abc".to_string()),
        challenge: "def".to_string(),
        r#type: "ghi".to_string(),
    };
    let client = reqwest::Client::new();
    let resp = client
        .post("http://127.0.0.1:8080/foo")
        .form(&params)
        .send()
        .await?;
    println!("{:#?}", resp);
    println!("{:?}", resp.text().await);
    Ok(())
}