连接到kubernetes mysql服务时，go-mysql连接被拒绝

I have a problem when connecting to a mysql instance with a go app using standard package. This is my connection string/log

    [13 Nov 16 13:53 +0000] [INFO] connecting to MySQL.. root:awsomepass@tcp(a-mysql-0:3340)/db?charset=utf8&parseTime=True&loc=Local
    2016/11/13 13:53:25 dial tcp 10.108.1.35:3340: getsockopt: connection refused

I tried

GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;

here is how I make connection, just basic, with string concatenation only

db, err := sql.Open("mysql", "root:awsomepass@tcp(a-mysql-0:3340)/db?charset=utf8&parseTime=True&loc=Local")
if err != nil {
    log.Fatal(err)
}

I can ping the service, connect to it with mysql-client from a different pod.

    # can connect without port for service
    / # mysql -u root -h a-mysql-0 -p
    Enter password:
    Welcome to the MariaDB monitor.  Commands end with ; or \g.
    Your MySQL connection id is 11
    Server version: 5.7.16 MySQL Community Server (GPL)

    Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.

    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    MySQL [(none)]> Ctrl-C -- exit!
    Aborted

    # can't' connect with port for service
    / # mysql -u root -h a-mysql-0:3340 -p
    Enter password:
    ERROR 2005 (HY000): Unknown MySQL server host 'a-mysql-0:3340' (-3)

and the mysql-service

    ➜  stg git:(develop) ✗ kubectl describe svc a-mysql-0
    Name:            a-mysql-0
    Namespace:        default
    Labels:            name=a-mysql-0
                tier=database
                type=mysql
    Selector:        name=a-mysql-0,tier=database
    Type:            ClusterIP
    IP:            None
    Port:            a-mysql-0    3340/TCP
    Endpoints:        10.108.1.35:3340
    Session Affinity:    None
    No events.

Is there anything I have missed or permission?