如何使用Golang获取UTC时间的时间戳？

I want to convert UTC time string to unix timestamp. I do this

fmt.Printf("%s %d
", time.Now().String(), time.Now().Unix())
fmt.Printf("%s %s
", time.Now().UTC().String(), time.Now().UTC().Unix())

1499018765

2017-07-02 20:06:05.5582802 +0200 CEST 1499018765

2017-07-02 18:06:05.791337 +0000 UTC 1499018765