pub fn set_ipv6_first(&mut self, ipv6_first: bool) {
        let context = Arc::get_mut(&mut self.context).expect("cannot set ipv6_first on a shared context");
        context.set_ipv6_first(ipv6_first);
    }
Try to connect IPv6 addresses first if hostname could be resolved to both IPv4 and IPv6
crates/shadowsocks-service/src/server/context.rs