How do I copy a file without overwriting an existing file in golang?

I have the below code that copies a text file from a directory to another with overwriting the file if exists 


What I'm looking for is to copy the file to the destination directory without overwriting, but keep both files. As in Windows for example, a copy of a file named "test" many times would be

test
test - Copy
test - Copy (2)
test - Copy (3)
text
text- Copy
text- Copy (2)
text- Copy (3) 


Any help would be appreciated ?

package main

import (
	"fmt"
	"io/ioutil"
	"log"
)

func main() {

	src := "./word1.txt"
	dest := "./words2.txt"

	bytesRead, err := ioutil.ReadFile(src)

	if err != nil {
		log.Fatal(err)
	}

	err = ioutil.WriteFile(dest, bytesRead, 0644)
	fmt.Println("Copied file \n")

	if err != nil {
		log.Fatal(err)
	}
}