It might be easier to do: let config: HashMap<String, String> = serde_json::from_reader(file) .expect("config has invalid json"); This means that you

It might be easier to do: let config: HashMap<String, String> = serde_json::from_reader(file) .expect("config has invalid json"); This means that you can just do let jenkins_server = config.get("jenkins_server") .expect("jenkins_server key not in config");