Rust Builder Pattern

#[derive(Debug)]
pub struct Request {
    pub url:     String,
    pub method:  String,
    pub body:    Option<String>,
    pub timeout: u32,
}

#[derive(Default)]
pub struct RequestBuilder {
    url:     String,
    method:  String,
    body:    Option<String>,
    timeout: u32,
}

impl RequestBuilder {
    pub fn new(url: impl Into<String>) -> Self {
        Self {
            url:     url.into(),
            method:  "GET".into(),
            timeout: 30,
            ..Default::default()
        }
    }

    pub fn method(mut self, m: impl Into<String>) -> Self {
        self.method = m.into(); self
    }

    pub fn body(mut self, b: impl Into<String>) -> Self {
        self.body = Some(b.into()); self
    }

    pub fn timeout(mut self, secs: u32) -> Self {
        self.timeout = secs; self
    }

    pub fn build(self) -> Request {
        Request {
            url:     self.url,
            method:  self.method,
            body:    self.body,
            timeout: self.timeout,
        }
    }
}