如何使用Go驱动程序从Bot中发送Mattermost中的直接消息？

package main

import (
    "fmt"
    "github.com/mattermost/mattermost-server/model"
    "github.com/mattermost/mattermost-server/plugin"
)

func main() {
    // 设置Mattermost服务器地址和认证信息
    serverURL := "https://your-mattermost-server.com"
    botToken := "your-bot-access-token"

    // 创建Mattermost客户端对象
    client := model.NewAPIv4Client(serverURL)
    client.SetToken(botToken)

    // 获取目标用户或频道的ID
    userId := getUserIdByUsername(client, "target_user")
    channelId := getChannelIdByName(client, "target_channel")

    // 发送直接消息
    post := &model.Post{
        UserId:    userId,
        ChannelId: channelId,
        Message:   "Hello, this is a direct message from the bot!",
    }
    _, resp := client.CreatePost(post)
    if resp.Error != nil {
        fmt.Println("Failed to send direct message:", resp.Error)
        return
    }

    fmt.Println("Direct message sent successfully!")
}

// 通过用户名获取用户ID
func getUserIdByUsername(client *model.Client4, username string) string {
    user, resp := client.GetUserByUsername(username, "")
    if resp.Error != nil {
        fmt.Println("Failed to get user ID:", resp.Error)
        return ""
    }
    return user.Id
}

// 通过频道名获取频道ID
func getChannelIdByName(client *model.Client4, channelName string) string {
    channel, resp := client.GetChannelByName(channelName, "")
    if resp.Error != nil {
        fmt.Println("Failed to get channel ID:", resp.Error)
        return ""
    }
    return channel.Id
}