Is there a built in function in go for making copies of arbitrary maps?

Is there a built in function in go for making copies of arbitrary maps?

I would be able to write one by hand but I found out earlier I was looking a similar question when I wanted to make a deep comparison of maps and there seemed to be a function already built in for that! So similarly, maybe I was wondering if there was an built in or some library or package for making deep copies of maps in golang. I am sure I am not the first person to want to make copies of maps in go.

By copy I mean you can create two different variables that reference a different map in memory even though they are the same content wise.

For a more general answer, you can encode your map and decode it in a new variable with encoding/gob.

The advantages of this way is that it'll even work on more complex data structure, like a slice of struct containing a slice of maps.

package main
import (
	"bytes"
	"encoding/gob"
	"fmt"
	"log"
)
func main() {
	ori := map[string]int{
		"key":  3,
		"clef": 5,
	}
	var mod bytes.Buffer
	enc := gob.NewEncoder(&mod)
	dec := gob.NewDecoder(&mod)
	fmt.Println("ori:", ori) // key:3 clef:5
	err := enc.Encode(ori)
	if err != nil {
		log.Fatal("encode error:", err)
	}
	var cpy map[string]int
	err = dec.Decode(&cpy)
	if err != nil {
		log.Fatal("decode error:", err)
	}
	fmt.Println("cpy:", cpy) // key:3 clef:5
	cpy["key"] = 2
	fmt.Println("cpy:", cpy) // key:2 clef:5
	fmt.Println("ori:", ori) // key:3 clef:5
}

If you want to know more about gobs, there is a go blog post about it.

No, there is no built-in one-liner for map deep copy.

However, there is an iterative solution as well as a generic package for deep copy.

Copying a map is a few, trivial lines of code. Just write the code and enjoy letting go of the idea that every simple piece of code has to be in a library!

original := map[string]int{
    "Hello": 4,
    "World": 123,
}
copy := map[string]int{}
for k, v := range original {
    copy[k] = v
}