list.Remove issue

main.go

package main

import (
	"container/list"
	"fmt"
)

type FirstUnique struct {
	nums []int
	m    map[int]*list.Element
	l    *list.List
}

func Constructor(nums []int) FirstUnique {
	m := map[int]*list.Element{}
	l := new(list.List)

	for _, n := range nums {
		if node, ok := m[n]; ok {
			l.Remove(node)
		} else {
			element := &list.Element{Value: n}
			l.PushBack(element)
			m[n] = element
		}
	}

	return FirstUnique{
		nums: nums,
		m:    m,
		l:    l,
	}
}

func (this *FirstUnique) ShowFirstUnique() int {
	return this.l.Front().Value.(*list.Element).Value.(int)
}

func (this *FirstUnique) Add(value int) {
	this.nums = append(this.nums, value)
	if node, ok := this.m[value]; ok {
		this.l.Remove(node)
	} else {
		element := &list.Element{Value: value}
		this.l.PushBack(element)
		this.m[value] = element
	}
}

func main() {
	obj := Constructor([]int{3, 5, 2, 3})

	fmt.Println(obj.ShowFirstUnique())

	obj.Add(2)

	fmt.Println(obj.ShowFirstUnique())

	obj.Add(3)
	obj.Add(5)

	fmt.Println(obj.ShowFirstUnique())
}