删除数组中某一个元素，并返回删除的元素地址

manager.go

package library

import (
	"errors"
	"fmt"
)

type MusicEntry struct {
	Id     string
	Name   string
	Artist string
	Source string
	Type   string
}

type MusicManager struct {
	musics []MusicEntry
}

func NewMusicManager() *MusicManager {
	return &MusicManager{make([]MusicEntry, 0)}
}

func (m *MusicManager) Len() int {
	return len(m.musics)
}

func (m *MusicManager) Remove(index int) *MusicEntry {
	if index < 0 || index >= len(m.musics) {
		return nil
	}

	removeMusic := &m.musics[index]                 // 修改为removeMusic := m.musics[index]，下面return &removeMusic就没有问题
	fmt.Println("RemoveMusic.Id:", removeMusic.Id)  // 输出 2

	if index == 0 {
		m.musics = m.musics[1:]
	} else if index == len(m.musics)-1 {
		m.musics = m.musics[:index]
	} else {
		m.musics = append(m.musics[:index], m.musics[index+1:]...)
	}
	fmt.Println("RemoveMusic.Id:", removeMusic.Id)  // 输出 3

	return removeMusic
}

func (m *MusicManager) Add(music *MusicEntry) {
	m.musics = append(m.musics, *music)
}

manager_test.go

package library

import (
	"fmt"
	"testing"
)

func TestOps(t *testing.T) {
	mm := NewMusicManager()
	if mm == nil {
		t.Error("NewMusicManager failed")
	}

	if mm.Len() != 0 {
		t.Error("NewMusicManager failed, not empty")
	}

	m0 := &MusicEntry{"1", "My heart will go on", "Celion Dion", "http://qbox/12321321", "mp3"}
	m1 := &MusicEntry{"2", "In Your Arms", "Stanfour", "http://qbox/221313", "wav"}
	m2 := &MusicEntry{"3", "Love", "Peter", "http://qbox/123", "mp3"}
        mm.Add(m0)
	mm.Add(m1)
	mm.Add(m2)

	if mm.Len() != 3 {
		t.Error("MusicManager.Add() failed")
	}

	mRemoved := mm.Remove(1)

	if mm.Len() != 2 {
		t.Error("MusicManager.Remove() failed")
	}

	if mRemoved == nil || mRemoved.Id != m1.Id {
		t.Error("MusicManager.Remove() failed")  // 此处报错
	}
}