Can't put value into map

I just learn golang, and want to build an struct like this.

{end:false map["h":{false "h" map["e":{true "e" map[]}]}
           "s":{false "s" map["h":{false "h" map["e":{true "e" map[]}]}]}
]}

Follow is the code I write:

package main

import "fmt"
type node struct {
	end      bool
	char     string
	children map[int32]node
}

func addKeyword(root *node, key string) {
	current := root
	for _, v := range key {
		mm := current.children
		if nil == mm || len(mm) == 0 {
			mm = make(map[int32]node)
			current.children = mm
		}
		child, ok := mm[v]
		if !ok {
			child = node{false, string(v), nil}
			mm[v] = child
		}
		current = &child
	}
	current.end = true
}

func main() {
	root := new(node)
	addKeyword(root, "he")
	addKeyword(root, "she")
	fmt.Println(root)
}

I get result is:

{end:false map["h":{false "h" map[]}
           "s":{false "s" map[]}
]}

I don't know why second level struct not append to root object.

The problem is related to the type of children map. You are using node values in this map. As a result, you get new values every time you access a key and the changes are not reflected into the original 'parent' node.

The fault lies with this line:

child, ok := mm[v]

child is a new variable that is equal to the value of node mm[v]. The changes you make happen to this value while the node value in mm remains unchanged.

To fix this problem, you can use *node for values in children:

type node struct {
    end      bool
    char     string
    children map[int32]*node
}

And fix the code accordingly:

// ...
mm := current.children
if nil == mm {
    mm = make(map[int32]*node)
    current.children = mm
}
child, ok := mm[v]
if !ok {
	child = &node{false, string(v), nil}
	mm[v] = child
}
current = child
// ...

Working example: https://play.golang.org/p/XcmPY4Nx-O