Go maps.Copy

maps.Copy is a function from the Go maps package, introduced in Go 1.21, which provides generic utilities for working with maps.

📘 maps.Copy – What it does

func Copy[K comparable, V any](dst, src map[K]V)

• Purpose: Copies key-value pairs from src into dst.
• If key exists in dst, the value will be overwritten.
• If dst is nil, a panic occurs.
• src can be nil, in which case it does nothing.

✅ Example

package main

import (
    "fmt"
    "maps"
)

func main() {
    src := map[string]int{"a": 1, "b": 2}
    dst := map[string]int{"b": 99, "c": 3}

    maps.Copy(dst, src)

    fmt.Println(dst) // Output: map[a:1 b:2 c:3]
}

• Key "b" gets overwritten from 99 to 2.
• Key "a" is added.
• Key "c" remains untouched.

⚠️ Notes

• Go version requirement: Must be using Go 1.21 or later.
• It does not return a new map, it modifies dst in-place.
• Use maps.Clone if you want to copy into a new map.