Why can't I initialize a map with new() in Go?

Question

package main

import \"fmt\"

func main() {
    p := new(map[string]int)
    m := make(map[string]int)
    m[\"in m\"] = 2
    (*p)[\"in p\"] = 1
    fmt.Println(m)
             


        

Answer 1

This is not directly an issue with new keyword. You would get the same behavior, if you did not initialize your map, when declaring it with var keyword, for example:

var a map[string]int
a["z"] = 10

The way to fix this is to initialize the map:

var a map[string]int
a = map[string]int{}
a["z"] = 10

And it works the same way, with new keyword:

p := new(map[string]int)
*p = map[string]int{}
(*p)["in p"] = 1 

The reason make(map[string]int) does what you expect is that the map is declared and initialized.

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