You should run the container in the command below:
docker run -d -v yourconfig.json:/etc/shadowsocks.json -p 9999:9999 --name shadowsocks playniuniu/shadowsocks
Remeber to replace your password
{
"server": "0.0.0.0",
"server_port": 9999,
"local_port": 1080,
"password": "YOUR PASSWORD",
"timeout": 300,
"method": "aes-256-cfb"
}