use and_then
use and_then

shadowsocks/shadowsocks-rust,zonyitoo/shadowsocks-rust,cch123/shadowsocks-rust,shadowsocks/shadowsocks-rust,shadowsocks/shadowsocks-rust,jessiex/shadowsocks-rust,jessiex/shadowsocks-rust,cch123/shadowsocks-rust,shadowsocks/shadowsocks-rust