Confuse on construct cookies and pass them into reqwest::Client

You need to import the CookieJar trait to access those methods.

// Create a cookie jar we can share with the HTTP client
let jar = Arc::new(Jar::default());

// create the HTTP client
let client = Client::builder()
    .cookie_provider(Arc::clone(&jar))
    .cookie_store(true)
    .build()
    .unwrap();

// Add some cookies
let cookie = HeaderValue::from_static(
    "password=my_super_secret_password; Expires=Thu, 21 Oct 2021 07:28:00 GMT; Secure; HttpOnly",
);
let url = "https://example.com".parse().unwrap();
jar.set_cookies(&mut [cookie].iter(), &url);

(playground)