curl -k https://dnsapi.cn/Domain.List -d "login_email=xxx&login_password=xxx" 

curl -k https://dnsapi.cn/Record.List -d "login_email=xxx&login_password=xxx&domain_id=xxx"

package dnspod

import (
	"io/ioutil"
	"net/http"
	"net/url"
	"strings"
)

const (
	login_email    = "<your_login_email>"
	login_password = "<your_login_password>"
	format         = "json"
	domain_id      = "<domain_id>"
	record_id      = "<record_id>"
	sub_domain     = "<your_subdomain>"
	record_type    = "CNAME"
	record_line    = "默认"
	ttl            = "600"
)

func Update(client *http.Client, cname string) string {
	body := url.Values{
		"login_email":    {login_email},
		"login_password": {login_password},
		"format":         {format},
		"domain_id":      {domain_id},
		"record_id":      {record_id},
		"sub_domain":     {sub_domain},
		"record_type":    {record_type},
		"record_line":    {record_line},
		"value":          {cname},
		"ttl":            {ttl},
	}
	req, err := http.NewRequest("POST", "https://dnsapi.cn/Record.Modify", strings.NewReader(body.Encode()))
	req.Header.Set("Accept", "text/json")
	req.Header.Set("Content-type", "application/x-www-form-urlencoded")
	resp, err := client.Do(req)
	if err != nil {
		return err.Error()
	}
	defer resp.Body.Close()
	bytes, _ := ioutil.ReadAll(resp.Body)
	return string(bytes)
}

var screen_chan chan int
var switch_chan = make(chan bool)

func main() {
	//a goroutine： 检查按键是否被按
	go func() {
		last_time := time.Now().UnixNano() / 1000000
		btn_pushed := 0
		total_mode := 3
		for msg := range WiringPiISR(PIN_GPIO_6, INT_EDGE_FALLING) {
			if msg > -1 {
				n := time.Now().UnixNano() / 1000000
				delta := n - last_time
				if delta > 300 { //如果两次按键变化的间隔时间<300ms，是因为接触信号不稳定可以忽略掉
					last_time = n
					btn_pushed++
					screen_chan <- btn_pushed % total_mode
				}
			}
		}
	}()

	//a goroutine： 根据管道消息刷新屏幕
	go loop_update_display()

	//选择确实的屏幕内容脚本编号
	screen_chan <- 0

	//a goroutine: 定时5s向管道发送更新屏幕内容的信号
	ticker := time.NewTicker(5 * time.Second)
	go func() {
		for {
			<-ticker.C
			screen_chan <- -1
		}
	}()
	
	...	
}

func loop_update_display() {
	current_screen := 0
	for msg := range screen_chan {
		switch_screen := false
		if msg >= 0 {
		   //说明是按钮触发的消息，而不是定时器触发的(-1)
			if msg != current_screen {
				//btn pushed
				current_screen = msg
				switch_screen = true
				go func() {
					select {
					case <-time.After(500 * time.Millisecond):
						display_loading()
						<-switch_chan
					case <-switch_chan:
					}
				}()
			}
		}
		switch current_screen {
		case 0:
			display_screen0()
		case 1:
			display_screen1()
		case 2:
			display_screen2()
		}
		if switch_screen {
			switch_chan <- true
		}
	}
}

go func() {
	select {
	case <-time.After(500 * time.Millisecond):
		display_loading(current_screen)
		<-switch_chan
	case <-switch_chan:
	}
}()

package main

import (
	"log"
)

var a, b, c int

func main() {
	a = 1
	b = 2
	c = a + 2
	log.Println(a, b, c)
}

package main

import (
	"log"
)

var a, b, c int

func main() {
	go func() {
		a = 1
		b = 2
	}()
	go func() {
		c = a + 2
	}()
	log.Println(a, b, c)
}

package counter

import (
	"encoding/base64"
	"fmt"
	"time"
	"net/http"

	"appengine"
	"appengine/channel"
)

var GIF []byte

const (
	TOPIC = "counter"
)

func init() {
	GIF, _ = base64.StdEncoding.DecodeString("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7")
	
	
	http.HandleFunc("/beacon.gif", handler)
	http.HandleFunc("/new_token", handler_new_token)	
}

func handler(w http.ResponseWriter, r *http.Request) {
	context := appengine.NewContext(r)

	now := time.Now()
	expire := now.AddDate(30, 0, 0)
	zcookie, _ := r.Cookie("z")
	if zcookie == nil {
		zcookie = &http.Cookie{}
		zcookie.Name = "z"
		zcookie.Value = make_hash("<your_salt>", r.RemoteAddr, now.UnixNano())
		zcookie.Expires = expire
		zcookie.Path = "/"
		http.SetCookie(w, zcookie)
	}

	w.Header().Set("Content-type", "image/gif")
	w.Header().Set("Cache-control", "no-cache, must-revalidate")
	w.Header().Set("Expires", "Sat, 26 Jul 1997 05:00:00 GMT")

	fmt.Fprintf(w, "%s", GIF)

	channel.Send(context, TOPIC, zcookie.Value+"\n"+r.RemoteAddr+"\n"+r.Referer()+"\n"+r.UserAgent())
}

func handler_new_token(w http.ResponseWriter, r *http.Request) {
	c := appengine.NewContext(r)
	tok, err := channel.Create(c, TOPIC)	
	callback := r.FormValue("callback")	
	if err != nil {
		http.Error(w, "Couldn't create Channel", http.StatusInternalServerError)
		c.Errorf("channel.Create: %v", err)
		return
	}
	if callback == "" {
		w.Header().Set("Content-type", "text/javascript")
		fmt.Fprintf(w, "%s", tok)
	} else {
		fmt.Fprintf(w, callback+"('%s')", tok)
	}
}