思路：微信后台可以对指定用户进行回复，群发其实就是一个loop，so 模拟POST提交到微信 后台， 模拟登陆，即可突破群发每日一条限制。

直接上代码

/*
 *@author 菠菜君
 *@Version 0.1
 *@time 2013-10-30
 *@go语言实现模拟登陆微信公众平台，突破微信群发每日一条限制
 *@青岛程序员 微信订阅号	qdprogrammer
 *@Golang 微信订阅号	gostock
 *@关于青岛程序员的技术，创业，生活 分享。
 *@开源 https://github.com/philsong/
 */
package main

import (
	"crypto/md5"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"io/IoUtil"
	"log"
	"net/http"
	"net/url"
	"regexp"
	"strings"
)

type WebWeChat struct {
	token   string
	cookies []*http.Cookie
}

func NewWebWeChat() *WebWeChat {
	w := new(WebWeChat)
	return w
}

func (w *WebWeChat) login() bool {
	login_url := "https://mp.weixin.qq.com/cgi-bin/login?lang=zh_CN"
	email := "songbohr@163.com"
	password := "xxx"
	h := md5.New()
	h.Write([]byte(password))
	password = hex.EncodeToString(h.Sum(nil))
	fmt.Println(password)
	post_arg := url.Values{"username": {email},"pwd": {password},"imgcode": {""},"f": {"json"}}

	fmt.Println(strings.NewReader(post_arg.Encode()))
	req,err := http.NewRequest("POST",login_url,strings.NewReader(post_arg.Encode()))
	req.Header.Set("Referer","https://mp.weixin.qq.com/")

	if err != nil {
		log.Fatal(err)
	}

	client := new(http.Client)
	resp,_ := client.Do(req)
	data,_ := IoUtil.ReadAll(resp.Body)

	s := string(data)
	fmt.Printf("%s",s)

	doc := json.NewDecoder(strings.NewReader(s))

	type Msg struct {
		Ret                     int
		ErrMsg                  string
		ShowVerifyCode,ErrCode int
	}

	var m Msg
	if err := doc.Decode(&m); err == io.EOF {
		fmt.Println(err)
	} else if err != nil {
		log.Println(err)
		return false
	}

	fmt.Println(m)

	if m.ErrCode == 0 || m.ErrCode == 65201 || m.ErrCode == 65202 {
		w.token = strings.Split(m.ErrMsg,"=")[3]

		fmt.Printf("token:%v\n",w.token)

		w.cookies = resp.Cookies()

		fmt.Println(w.cookies)
		return true
	}

	switch m.ErrCode {
	case -1:
		fmt.Println("系统错误，请稍候再试。")
	case -2:
		fmt.Println("帐号或密码错误。")
	case -3:
		fmt.Println("您输入的帐号或者密码不正确，请重新输入。")
	case -4:
		fmt.Println("不存在该帐户。")
	case -5:
		fmt.Println("您目前处于访问受限状态。")
	case -6:
		fmt.Println("请输入图中的验证码")
	case -7:
		fmt.Println("此帐号已绑定私人微信号，不可用于公众平台登录。")
	case -8:
		fmt.Println("邮箱已存在。")
	case -32:
		fmt.Println("您输入的验证码不正确，请重新输入。")
	case -200:
		fmt.Println("因频繁提交虚假资料，该帐号被拒绝登录。")
	case -94:
		fmt.Println("请使用邮箱登陆。")
	case 10:
		fmt.Println("该公众会议号已经过期，无法再登录使用。")
	case -100:
		fmt.Println("海外帐号请在公众平台海外版登录,<a href=\"http://admin.wechat.com/\">点击登录</a>")
	default:
		fmt.Println("未知的返回。")
	}

	return false
}

func (w *WebWeChat) SendTextMsg(fakeid string,content string) bool {
	send_url := "http://mp.weixin.qq.com/cgi-bin/singlesend"
	referer_url := "https://mp.weixin.qq.com/cgi-bin/singlesendpage?t=message/send&action=index&tofakeid=%s&token=%s&lang=zh_CN"

	post_arg := url.Values{
		"tofakeid": {fakeid},"type":     {"1"},"content":  {content},"ajax":     {"1"},"token":    {w.token},"t":        {"ajax-response"},}

	req,_ := http.NewRequest("POST",send_url,strings.NewReader(post_arg.Encode()))

	req.Header.Set("Referer",fmt.Sprintf(referer_url,fakeid,w.token))

	for i := range w.cookies {
		req.AddCookie(w.cookies[i])
	}

	client := new(http.Client)
	resp,_ := IoUtil.ReadAll(resp.Body)

	doc := json.NewDecoder(strings.NewReader(string(data)))

	type Msg struct {
		Ret string
		Msg string
	}

	var m Msg
	if err := doc.Decode(&m); err == io.EOF {
		fmt.Println(err)
	} else if err != nil {
		log.Fatal(err)
	}
	fmt.Println(m.Msg)

	if m.Msg == "ok" {
		return true
	}

	return false
}

func (w *WebWeChat) GetFakeId() bool {
	msg_url := "https://mp.weixin.qq.com/cgi-bin/contactmanage?t=user/index&pagesize=10&pageidx=0&type=0&groupid=0&token=%s&lang=zh_CN"
	referer_url := "https://mp.weixin.qq.com/cgi-bin/home?t=home/index&lang=zh_CN&token=%s"

	req,_ := http.NewRequest("GET",fmt.Sprintf(msg_url,w.token),nil)

	req.Header.Set("Referer",_ := IoUtil.ReadAll(resp.Body)

	//fmt.Println(string(data))
	fmt.Println(string(data))
	re := regexp.MustCompile(`(?s)(?U)contacts.+contacts`)
	list := re.FindString(string(data))
	list = strings.Replace(list,`contacts`,"",-1)
	list = strings.Replace(list,``," ",-1)
	fmt.Println(list)

	list = strings.TrimLeft(list,"\":")
	list = strings.TrimRight(list,"}).")

	fmt.Println(list)

	return true
}

func main() {
	wechat := NewWebWeChat()

	if wechat.login() == true {
		log.Println(wechat.GetFakeId())
		tofakeid := "333215495" //my fakeid for test
		wechat.SendTextMsg(tofakeid,"Hello Phil.")
	} else {
		fmt.Println("wechat login Failed.")
	}
}