Go time.Now().UnixNano() convert to milliseconds?

Question

How can I get Unix time in Go in milliseconds?

I have the following function:

func makeTimestamp() int64 {     return time.Now().UnixNano() % 1e6 / 1e3 } 

I need less precision and only want milliseconds.

Answer 1

The 2021 answer:

As of go v1.17, the time package added UnixMicro() and UnixMilli(), so the correct answer would be: time.Now().UnixMilli()

Original answer:

Just divide it:

func makeTimestamp() int64 {     return time.Now().UnixNano() / int64(time.Millisecond) } 

Here is an example that you can compile and run to see the output

package main  import (     "time"     "fmt" )  func main() {     a := makeTimestamp()      fmt.Printf("%d \n", a) }  func makeTimestamp() int64 {     return time.Now().UnixNano() / int64(time.Millisecond) } 

Answer 2

As @Jono points out in @OneOfOne's answer, the correct answer should take into account the duration of a nanosecond. Eg:

func makeTimestamp() int64 {     return time.Now().UnixNano() / (int64(time.Millisecond)/int64(time.Nanosecond)) } 

OneOfOne's answer works because time.Nanosecond happens to be 1, and dividing by 1 has no effect. I don't know enough about go to know how likely this is to change in the future, but for the strictly correct answer I would use this function, not OneOfOne's answer. I doubt there is any performance disadvantage as the compiler should be able to optimize this perfectly well.

See https://en.wikipedia.org/wiki/Dimensional_analysis

Another way of looking at this is that both time.Now().UnixNano() and time.Millisecond use the same units (Nanoseconds). As long as that is true, OneOfOne's answer should work perfectly well.