如何通过go自定义一个分页插件

go get github.com/go-sql-driver/mysql 
go get github.com/jmoiron/sqlx

package sql

import (
	"back-me/main/util"
	"fmt"
	_ "github.com/go-sql-driver/mysql"
	"github.com/jmoiron/sqlx"
	"strings"
)

const (
	username = "root"
	password = "123456"
	host     = "localhost"
	port     = 3306
	dbname   = "fdis"
)


var Db *sqlx.DB

func init() {
	connectToDatabase()
}

// 连接数据库
func connectToDatabase() {
	dataSourceName := fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?parseTime=true&loc=Local", username, password, host, port, dbname)

	db, err := sqlx.Open("mysql", dataSourceName)
	if err != nil {
		util.Log.Error("sql connection error:" + err.Error())
	}

	// 检查是否连接成功
	err = db.Ping()
	if err != nil {
		util.Log.Error("sql connection error:" + err.Error())
	}
	Db = db
}

// 执行增删改操作
func ExecuteCUD(sql string, params ...interface{}) int64 {
	sql = jointSqlStr(sql, params...)
	conn, err := Db.Begin()
	if err != nil {
		util.Log.Error("Sql Error:" + err.Error())
		return -1
	}

	r, err := conn.Exec(sql)
	if err != nil {
		util.Log.Error("Sql Error:" + err.Error())
		conn.Rollback()
		return -1
	}
	id, err := r.LastInsertId()
	if err != nil {
		util.Log.Error("Sql Error:" + err.Error())
		conn.Rollback()
		return -1
	}
	conn.Commit()
	return id
}

// 执行select all
func ExecuteSelectAll(stc interface{}, sql string, params ...interface{}) error {
	sql = jointSqlStr(sql, params...)
	err := Db.Select(stc, sql)
	if err != nil {
		util.Log.Error("Sql Select Error:" + err.Error())
		return err
	}
	return nil
}



// 1 5 | 0 5
// 2 5 | 5 5
// 3 5 | 10 5

func jointSqlStr(sqlStr string, args ...interface{}) string {
	// 以%s分割
	strs := strings.Split(sqlStr, "%s")
	if len(strs) == 0 {
		return sqlStr
	}
	newSql := ""
	for i, _ := range strs {
		newSql += strs[i]
		if i != len(strs)-1 {
			switch args[i].(type) {
			case string:
				newSql += args[i].(string)
				break
			case int:
				newSql += fmt.Sprintf("%v", args[i].(int))
				break
			case uint:
				newSql += fmt.Sprintf("%v", args[i].(uint))
				break
			}
		}

	}
	return newSql
}

package page

import (
	"back-me/main/model"
	"errors"
	"reflect"
)

var PageError = errors.New("page or pageSize cannot be < 1")

type Pager struct {
	Page     int `json:"page"`
	PageSize int `json:"pageSize"`
}

func NewPager(page int, pageSize int) (*Pager, error) {
	if page < 1 || pageSize < 1 {
		return nil, PageError
	}
	return &Pager{
		page,
		pageSize,
	}, nil
}

func (p *Pager) SelectPage(data interface{}) *model.PageResult {
	page := p.Page
	pageSize := p.PageSize
	page = (page - 1) * pageSize
	start := page
	end := page + pageSize
	l := reflect.ValueOf(data).Elem().Len()

	if l-1 < start {
		return model.NewPageResult1(nil, 0, page, pageSize)
	} else if l-1 >= start && l-1 <= end {
		return model.NewPageResult1(subData(data, start, l), l, p.Page, p.PageSize)
	} else {
		return model.NewPageResult1(subData(data, start, end), l, p.Page, p.PageSize)
	}
}

// 包前不包后
func subData(data any, start int, end int) interface{} {
	v := reflect.ValueOf(data)
	v = v.Elem()
	return v.Slice(start, end).Interface()
}

package model

type PageResult struct {
	Data     any    `json:"data"`
	Code     int    `json:"code"`
	Mes      string `json:"mes"`
	Total    int    `json:"total"`
	Page     int    `json:"page"`
	PageSize int    `json:"pageSize"`
}

func NewPageResult(data any, code int, mes string, total int, page int, pageSize int) *PageResult {
	return &PageResult{
		data, code, mes, total, page, pageSize,
	}
}

// NewPageResult1
func NewPageResult1(data any, total int, page int, pageSize int) *PageResult {
	return NewPageResult(data, 200, "ok", total, page, pageSize)
}

func TestSelectPage(t *testing.T) {
	var userVos []vo.User // 查询出的数据,最终封装到这里面
	var sqlStr = "SELECT * FROM `tx_user`  WHERE PASSWORD  LIKE '%s' LIMIT 0, 2" // %s 就是占位符,被后面传入的参数替换
	sql.ExecuteSelectAll(&userVos, sqlStr, "%")
	// 分页
	// 0 1
	// 2 3
	// start <
	newPager, err := page.NewPager(1, 2)
	if err != nil {
		fmt.Println("error:", err.Error())
	}
	pageResult := newPager.SelectPage(&userVos)
	fmt.Println(pageResult)
}