为什么我不能将纪元时间转换为字符串？

I have the following program:

package main

import (
    "fmt"
    "time"
)

func main() {
    now := time.Now().UnixNano() / int64(time.Millisecond)
    nowString := string(now)
    fmt.Println(nowString)
}

I'm expecting the epoch time to be printed as a string. Instead I get:

�

How do I fix this error?

You are doing a lot of calculations which are not needed if you use time's functions as exemplified here - https://gobyexample.com/time-formatting-parsing

Also. if all you need to do is to print an integer, you don't have to convert it to a string but simply use a format specifier like:

func main() {
    now := time.Now().UnixNano() / int64(time.Millisecond)
    //now is an int64 as you may have observed
    fmt.Printf("%d", now)
    //or even fmt.Println(now)
}

main.go

package main

import "fmt"
import "time"

func main() {
    nanos := time.Now().UnixNano()
    fmt.Println(time.Unix(0, nanos))

    millis := nanos / 1000000
    fmt.Println(millis)
}