Logrus timestamp formatting

I'm trying to transition from the Golang log package to Logrus. My issue is around how to customize the timestamp format of logged messages. The default is a counter of seconds since start but I want a "2016-03-24 17:10:15" format. My simple test code is:

package main

import (
        "github.com/Sirupsen/logrus"
)

func main() {
        customFormatter := new(logrus.TextFormatter)
        customFormatter.TimestampFormat = "2006-01-02 15:04:05"
        logrus.SetFormatter(customFormatter)
        logrus.Info("Hello Walrus")
}

This compiles and runs fine but the timestamp format is unchanged. Can anyone offer some insight into why it isn't working?

Thanks