pub fn scheme(&self) -> String {
        match self.scheme {
            Some(ref p) => p.to_string(),
            None => match self.region {
                Region::Custom { ref endpoint, .. } => {
                    if endpoint.starts_with("http://") {
                        "http".to_owned()
                    } else {
                        "https".to_owned()
                    }
                }
                _ => "https".to_owned(),
            },
        }
    }
Returns the current http scheme (https or http)
rusoto/signature/src/signature.rs