go语言功能代码

一、数据类型转换

package main

import (
    "fmt"
    "strconv"
)

func main() {
    //int到string
    str := strconv.Itoa(int(1))
    fmt.Println("int转string", str)
    //int64到string
    str2 := strconv.FormatInt(int64(1), 10)
    fmt.Println("int64转string", str2)
    //float64转string formatFloat只能接收float64如果想用float32需要强转float64(float32(0.8))
    //下面是参数说明
    // 'b' (-ddddp±ddd，二进制指数)
    // 'e' (-d.dddde±dd，十进制指数)
    // 'E' (-d.ddddE±dd，十进制指数)
    // 'f' (-ddd.dddd，没有指数)
    // 'g' ('e':大指数，'f':其它情况)
    // 'G' ('E':大指数，'f':其它情况)
    str3 := strconv.FormatFloat(float64(0.8), 'f', -1, 32)
    fmt.Println("float32转string", str3)
    //string到int  有异常的都不进行处理这个后面说
    i, _ := strconv.Atoi("10")
    fmt.Println("strin转int", i)
    //string 到int64
    i64, _ := strconv.ParseInt("123", 10, 64)
    fmt.Println("strin转int64", i64)
    //string转float64 如果想转float32 用float32(fl32)强转一下就可以
    fl32, _ := strconv.ParseFloat("3.1415926535", 32/64)
    fmt.Println("strin转float64", fl32)
}

二、时间类型转换

package main

import (
    "fmt"
    "time"
)

func main() {
    //获取当前时间
    now := time.Now()
    //时间转化为string
    //在go语言里将日期格式化并不是yyyy-MM-dd HH:ss:mm 而是用"2006-01-02 15:04:05具体含义如下
    //月份 1,01,Jan,January
    //日　 2,02,_2
    //时　 3,03,15,PM,pm,AM,am
    //分　 4,04
    //秒　 5,05
    //年　 06,2006
    //周几 Mon,Monday
    //时区时差表示 -07,-0700,Z0700,Z07:00,-07:00,MST
    //时区字母缩写 MST
    timeStr := now.Format("2006-01-02 15:04:05")
    fmt.Println("日期类型当前时间: ", now)
    fmt.Println("字符串类型当前时间: ", timeStr)
    //string转化为时间
    date, _ := time.Parse("2006-01-02 15:04:05", "2017-08-29 08:37:18")
    fmt.Println("string转日期:", date)
    //判断两个时间先后
    trueOrFalse := date.After(now)
    if trueOrFalse == true {
        fmt.Println("2017-08-29 08:37:18在", timeStr, "之后")
    } else {
        fmt.Println("2017-08-29 08:37:18在", timeStr, "之前")
    }
    // ParseDuration parses a duration string.
    // A duration string is a possibly signed sequence of decimal numbers,
    // each with optional fraction and a unit suffix,
    // such as "300ms", "-1.5h" or "2h45m".
    //  Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
    // -代表时间之前,不加代表时间之后 m表示分钟,如20分钟前
    m, _ := time.ParseDuration("-20m")
    m1 := now.Add(m)
    fmt.Println("10分钟之前：", m1)
    // h代表小时 一天之前为-24h
    h, _ := time.ParseDuration("-8h")
    h1 := now.Add(h)
    fmt.Println("8小时之前", h1)
    //    // 一天前
    d, _ := time.ParseDuration("-24h")
    d1 := now.Add(d)
    fmt.Println(d1)
    //计算两个时间差几秒
    sec := now.Sub(m1)
    fmt.Println(sec.Seconds(), "秒")
    //计算两个时间差几分钟
    minutes := now.Sub(m1)
    fmt.Println(minutes.Minutes(), "分钟")
    //计算两个时间差几小时
    hours := now.Sub(h1)
    fmt.Println(hours.Hours(), "小时")
    //计算两个时间差几天
    day := now.Sub(d1)
    fmt.Println(day.Hours()/24, "天")
    //注意:splite3数据库中字段如果是datetime类型获取数据时格式转换会有问题
    //如2017-08-29 08:37:18这样的时间从数据库获取后会变成2017-08-29T08:37:18Z
    //进行格式转化之后不能比较，所以需要将T和Z替换为" "
    //不知道其他数据库有没有这样的问题
}

三、配置文件读取

package main

import (
    "flag"
    "sync"

    "github.com/larspensjo/config"
)

var Conf_Main_Topic = "DEFAULT"

var (
    //config.ini为配置文件格式为 key=value
    configFile = flag.String("configfile", "config.ini", "General configuration file")
)
var commonConf = make(map[string]string)
var lock sync.RWMutex

func LoadCommonConfiguration() {
    lock.Lock()
    defer lock.Unlock()
    cfg, err := config.ReadDefault(*configFile)
    if err != nil {
        //....
    }
    commonConf = make(map[string]string)
    if cfg.HasSection(Conf_Main_Topic) {
        section, err := cfg.SectionOptions(Conf_Main_Topic)
        if err != nil {
            //....
        }
        for _, v := range section {
            options, err := cfg.String(Conf_Main_Topic, v)
            if err != nil {
                //....
            }
            commonConf[v] = options
        }
    }
}

//通过GetConf方法将key传入获取value值
func GetConf(key string) string {
    lock.RLock()
    defer lock.RUnlock()
    return commonConf[key]
}

四、Json与Map转换

package main

import (
    "encoding/json"
    "strings"
    //    "github.com/bitly/go-simplejson" // for json get
)

//把两层嵌套结构的json格式的数据组转成map(map中不含interface结构)
func NoInterfaceJsonToMap(input string) (map[string]map[string]interface{}, error) {
    result := make(map[string]map[string]interface{})
    err := json.Unmarshal([]byte(input), &result)
    if err != nil {
        return nil, err
    }
    return result, nil
}
func MapToJson(input map[string]interface{}) (string, error) {
    result, err := json.Marshal(input)
    if err != nil {
        //        panic(err)
        return "", err
    }
    return string(result), nil
}

func MapMapToJson(input map[string]map[string]interface{}) (string, error) {
    result, err := json.Marshal(input)
    if err != nil {
        return "", err
    }
    return string(result), nil
}

func JsonToMap(input string) (map[string]interface{}, error) {
    result := make(map[string]interface{})
    err := json.Unmarshal([]byte(input), &result)
    if err != nil {
        return nil, err
    }
    return result, nil
}

func BoltKeyValueToJson(key, value string, delimeter string) (string, error) {
    keys := []string{key}
    values := []string{value}
    return BoltKeyValuesToJson(keys, values, delimeter)
}
func BoltKeyValuesToJson(keys, values []string, delimeter string) (string, error) {
    mapResult := make(map[string]interface{})
    for i := range keys {
        key := strings.Split(keys[i], delimeter)
        value := values[i]
        cur := mapResult
        for j := range key {
            if j == len(key)-1 {
            } else if j == len(key)-2 {
                if cur[key[j]] == nil {
                    cur[key[j]] = map[string]string{key[len(key)-1]: value}
                } else {
                    cur[key[j]].(map[string]string)[key[len(key)-1]] = value
                }
            } else {
                if cur[key[j]] == nil {
                    cur[key[j]] = make(map[string]interface{})
                }
                cur = cur[key[j]].(map[string]interface{})
            }
        }
    }
    return MapToJson(mapResult)
}

五、通过JSON数据发送Email

package main

import (
    "bytes"
    "errors"
    "fmt"
    "io/ioutil"
    "net/http"
    "strconv"
    "strings"
)

func HttpPostByJSON(accessUrl string, json string, redo int) error {
    fmt.Println(json)
    fmt.Println("post write json bytes:" + strconv.Itoa(len(json)))
    for j := 1; j <= redo; j++ {
        req_new := bytes.NewBuffer([]byte(json))
        request, err := http.NewRequest("POST", accessUrl, req_new)
        if err == nil {
            request.Header.Set("Content-Type", "application/json;charset=UTF-8")
            client := http.Client{}
            response, err1 := client.Do(request)
            if err1 == nil {
                body, err := ioutil.ReadAll(response.Body)
                if err != nil {
                    fmt.Println("Unknown error in sending Email")
                } else {
                    resp := string(body)
                    if strings.Contains(resp, "\"code\":\"200\"") {
                        return nil
                    } else {
                        fmt.Println(string(body))
                    }
                }
            } else {
                fmt.Println(err1)
            }
        } else {
            fmt.Println(err)
        }
    }
    return errors.New("Fail to send email notification")
}

六、文件读写删除操作

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "strings"
)
func FileExist(filename string) bool {
    _, err := os.Stat(filename)
    if os.IsNotExist(err) {
        return false
    }
    fmt.Println(err)
    return err == nil || os.IsExist(err)
}

func ReadFileByLine(filename string) []string {
    if !FileExist(filename) {
        return []string{}
    }
    f, err := os.Open(filename)
    fmt.Println(err)
    defer f.Close()
    rd := bufio.NewReader(f)
    result := []string{}
    for {
        line, err := rd.ReadString('\n')
        if err == nil || io.EOF == err {
            line = strings.TrimSpace(line)
            if len(line) > 0 {
                result = append(result, line)
            }
        }
        if io.EOF == err {
            break
        }
        fmt.Println(err)
    }
    return result
}

func WriteFileByLine(filename string, data []string) {
    f, err := os.Create(filename)
    fmt.Println(err)
    defer f.Close()
    wt := bufio.NewWriter(f)
    for i := range data {
        _, err := wt.WriteString(data[i])
        if io.EOF == err {
            break
        }
        fmt.Println(err)
    }
    wt.Flush()
}

func DeleteFile(filename string) {
    if FileExist(filename) {
        err := os.Remove(filename)
        fmt.Println(err)
    }
}

七、go执行linux和windows命令操作

package main

import (
    "errors"
    "fmt"
    "os/exec"
    "runtime"
    "strings"
)

func runInLinux(cmd string) string {
    fmt.Println("Running Linux Cmd:" + cmd)
    result, err := exec.Command("/bin/sh", "-c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result))
}

func runInWindows(cmd string) string {
    fmt.Println("Running Win Cmd:" + cmd)
    result, err := exec.Command("cmd", "/c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result))
}

func RunCommand(cmd string) string {
    if runtime.GOOS == "windows" {
        return runInWindows(cmd)
    } else {
        return runInLinux(cmd)
    }
}

func RunLinuxCommand(cmd string) string {
    if runtime.GOOS == "windows" {
        return ""
    } else {
        return runInLinux(cmd)
    }
}

func runInLinuxWithErr(cmd string) (string, error) {
    fmt.Println("Running Linux Cmd:" + cmd)
    result, err := exec.Command("/bin/sh", "-c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result)), err
}

func runInWindowsWithErr(cmd string) (string, error) {
    fmt.Println("Running Win Cmd:" + cmd)
    result, err := exec.Command("cmd", "/c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result)), err
}

func RunCommandWithErr(cmd string) (string, error) {
    if runtime.GOOS == "windows" {
        return runInWindowsWithErr(cmd)
    } else {
        return runInLinuxWithErr(cmd)
    }
}

func RunLinuxCommandWithErr(cmd string) (string, error) {
    if runtime.GOOS == "windows" {
        return "", errors.New("could not run in windows OS")

    } else {
        return runInLinuxWithErr(cmd)
    }
}

八、异常处理

Golang 有2个内置的函数 panic() 和 recover()，用以报告和捕获运行时发生的程序错误，与 error 不同，panic-recover 一般用在函数内部。一定要注意不要滥用 panic-recover，可能会导致性能问题，我一般只在未知输入和不可靠请求时使用。

golang 的错误处理流程：当一个函数在执行过程中出现了异常或遇到 panic()，正常语句就会立即终止，然后执行 defer 语句，再报告异常信息，最后退出 goroutine。如果在 defer 中使用了 recover() 函数,则会捕获错误信息，使该错误信息终止报告。

package main
import (
 "log"
 "strconv"
)
//捕获因未知输入导致的程序异常
func catch(nums ...int) int {
 defer func() {
  if r := recover(); r != nil {
   log.Println("[E]", r)
  }
 }()
 return nums[1] * nums[2] * nums[3] //index out of range
}
//主动抛出 panic，不推荐使用，可能会导致性能问题
func toFloat64(num string) (float64, error) {
 defer func() {
  if r := recover(); r != nil {
   log.Println("[W]", r)
  }
 }()
 if num == "" {
  panic("param is null") //主动抛出 panic
 }
 return strconv.ParseFloat(num, 10)
}
func main() {
 catch(2, 8)
 toFloat64("")
}

go语言有异常的返回会有两个返回参数包括值跟error，判断error是否为nil进行相应处理就可以最好不要panic

十、数据库操作

package main

import (
    "database/sql"
    "errors"
    "fmt"
    "sync"

    _ "github.com/mattn/go-sqlite3"
)

var db *sql.DB
var dbLock sync.Mutex

func main() {
    //查询调用RunQuery或者RunQueryWithErr
    //?为占位符对应相应参数
    rows := RunQuery("select age from table where id = ? and name = ?", 1, "abc")
    //也可以使用struct构建对象,获取数据库字段时需要用sql.Null...否则取空值会报错
    var age sql.NullInt64
    var ages []Int64

    //如果有多条返回值用for循环遍历,如果确定只有一条可以用if,这里只有一条所以用if,也可以将if改为for
    if rows.Next() {
        err := rows.Scan(&age)
        if err != nil {
            //........
        }
        //sql.NullInt64中有两个方法Int64和Valid,Valid用来判断值是否为空返回值为true、false
        //Int64为实际值,sql.NullInt64对象如果为空Int64值为0
        if age.Valid {
            //对获取到的age做操作
            fmt.Println(age.Int64)
        }
    }
    //sqlite3中使用完rows之后一定要调用close释放锁,否则继续调用数据库语句会报数据库被锁的异常
    rows.Close()
    //sqlite3中查询和增删改不能同时进行,也会报数据库被锁的异常
    //需要在查询之后统一进行增删改操作,增删改调用ExecSQL或ExecSqlWithErr
}

func OpenDB() {
    var err error
    //foo.db为数据库名字
    db, err = sql.Open("sqlite3", "./foo.db?_txlock=exclusive")
    fmt.Println(err)
    _, err = db.Exec("PRAGMA synchronous = OFF;")
    fmt.Println(err)
}

func CloseDB() {
    if db != nil {
        err := db.Close()
        db = nil
        fmt.Println(err)
    }
}

func ExecSQL(query string, args ...interface{}) sql.Result {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    if query == "" {
        panic("Empty sql input")
    }
    fmt.Println("Running Exec:")
    fmt.Println(query)
    fmt.Println(args...)
    res, err := db.Exec(query, args...)
    fmt.Println(err)
    return res
}

func RunQuery(query string, args ...interface{}) *sql.Rows {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    if query == "" {
        panic("Empty sql input")
    }
    fmt.Println("Running Query:")
    fmt.Println(query)
    fmt.Println(args...)
    res, err := db.Query(query, args...)
    fmt.Println(err)
    return res
}
//多条语句的事物操作
func ExecTransaction(querys []string, args [][]string) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    tx, err := db.Begin()
    fmt.Println(err)
    fmt.Println("Running Trans:")
    for index, query := range querys {
        if query == "" {
            panic("Empty sql input")
        }
        oldArgs := args[index]
        newArgs := make([]interface{}, len(oldArgs))
        for i, v := range oldArgs {
            newArgs[i] = interface{}(v)
        }
        fmt.Println(query)
        fmt.Println(newArgs...)
        _, err := tx.Exec(query, newArgs...)
        fmt.Println(err)
    }
    err = tx.Commit()
    fmt.Println(err)
}

func OpenDBWithErr() error {
    var err error
    db, err = sql.Open("sqlite3", "./pjm.db?_txlock=exclusive")
    if err != nil {
        return err
    }
    _, err = db.Exec("PRAGMA synchronous = OFF;")
    return err
}

func CloseDBWithErr() error {
    if db != nil {
        err := db.Close()
        db = nil
        return err
    }
    return nil
}

func ExecSQLWithErr(query string, args ...interface{}) (sql.Result, error) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        err := OpenDBWithErr()
        if err != nil {
            return nil, err
        }
    }
    if query == "" {
        return nil, errors.New("Empty sql input")
    }
    fmt.Println("Running Exec With Err:")
    fmt.Println(query)
    fmt.Println(args...)
    return db.Exec(query, args...)
}

func RunQueryWithErr(query string, args ...interface{}) (*sql.Rows, error) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        err := OpenDBWithErr()
        if err != nil {
            return nil, err
        }
    }
    if query == "" {
        return nil, errors.New("Empty sql input")
    }
    fmt.Println("Running Query With Err:")
    fmt.Println(query)
    fmt.Println(args...)
    return db.Query(query, args...)
}

func ExecTransactionWithErr(querys []string, args [][]string) error {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        err := OpenDBWithErr()
        if err != nil {
            return err
        }
    }
    tx, err := db.Begin()
    if err != nil {
        return err
    }
    fmt.Println("Running Trans With Err:")
    for index, query := range querys {
        if query == "" {
            return errors.New("Empty sql input")
        }
        oldArgs := args[index]
        newArgs := make([]interface{}, len(oldArgs))
        for i, v := range oldArgs {
            newArgs[i] = interface{}(v)
        }
        fmt.Println(query)
        fmt.Println(newArgs...)
        _, err := tx.Exec(query, newArgs...)
        if err != nil {
            return err
        }
    }
    return tx.Commit()
}

十一、go语言web编程

package main

import (
    "fmt"
    "html/template"
    "log"
    "net/http"
    "strings"
)

func sayhelloName(w http.ResponseWriter, r *http.Request) {
    r.ParseForm() //解析url传递的参数，对于POST则解析响应包的主体（request body）
    //注意:如果没有调用ParseForm方法，下面无法获取表单的数据
    fmt.Println(r.Form) //这些信息是输出到服务器端的打印信息
    fmt.Println("path", r.URL.Path)
    fmt.Println("scheme", r.URL.Scheme)
    fmt.Println(r.Form["url_long"])
    for k, v := range r.Form {
        fmt.Println("key:", k)
        fmt.Println("val:", strings.Join(v, ""))
    }
    fmt.Fprintf(w, "Hello astaxie!") //这个写入到w的是输出到客户端的
}

func login(w http.ResponseWriter, r *http.Request) {
    fmt.Println("method:", r.Method) //获取请求的方法
    //Handler里面是不会自动解析form的，必须显式的调用r.ParseForm()后，才能对这个表单数据进行操作
    r.ParseForm()
    if r.Method == "GET" {
        t, _ := template.ParseFiles("login.html")
        t.Execute(w, nil)
    } else {
        //请求的是登陆数据，那么执行登陆的逻辑判断
        fmt.Println("username:", r.Form["username"])
        fmt.Println("password:", r.Form["password"])
        //获取username的值需要[0]
        if r.Form["username"][0] == "abc" {
            //如果username为abc跳转到user.html页面打印abc=====
            t, _ := template.ParseFiles("./user.html")
            //t.Execute第二个参数可以传各种类型的数据到页面
            t.Execute(w, "abc=====")
        } else if r.Form["username"][0] == "efg" {
            t, _ := template.ParseFiles("./userMap.html")
            result := map[string]string{}
            result["key"] = "value"
            //返回map
            t.Execute(w, result)
        } else {
            t, _ := template.ParseFiles("./userMaps.html")
            result := []map[string]string{}
            m1 := map[string]string{}
            m2 := map[string]string{}
            m3 := map[string]string{}
            m1["a1"] = "111"
            m1["a2"] = "222"
            m1["a3"] = "333"
            m1["a4"] = "444"
            m2["a1"] = "555"
            m2["a2"] = "666"
            m2["a3"] = "777"
            m2["a4"] = "888"
            m3["a1"] = "999"
            m3["a2"] = "123"
            m3["a3"] = "456"
            m3["a4"] = "789"
            result = append(result, m1, m2, m3)
            //返回多个map
            t.Execute(w, result)
        }
    }
}

func main() {
    http.HandleFunc("/", sayhelloName)       //设置访问的路由
    http.HandleFunc("/login", login)         //设置访问的路由
    err := http.ListenAndServe(":9090", nil) //设置监听的端口
    if err != nil {
        log.Fatal("ListenAndServe: ", err)
    }
}

login.html页面

<html>
<head>
<title></title>
</head>
<body>
<form action="/login" method="post">
    用户名:<input type="text" name="username">
    密码:<input type="password" name="password">
    <input type="submit" value="登陆">
</form>
</body>
</html>

user.html页面

go语言中页面获取值必须加{{ }}

<html>
<head>
<title></title>
</head>
<body>
从后台获取的值为: {{.}}
</body>
</html>

userMap.html页面

<html>
<head>
<title></title>
</head>
<body>
从后台获取的值为: {{.key}}
</body>
</html>

userMaps.html页面

<html>
<head>
<title></title>
</head>
<body>
{{range $index,$re :=.}}
{{$re.a1}}</br>
{{$re.a2}}</br>
{{$re.a3}}</br>
{{$re.a4}}</br>
{{end}}
</body>
</html>

十二、分页实现

//分页方法，根据传递过来的页数，每页数，总数，返回分页的内容 7个页数 前 1，2，3，4，5 后 的格式返回,小于5页返回具体页数
func Paginator(page, prepage int, nums int64) map[string]interface{} {

    var firstpage int //前一页地址
    var lastpage int  //后一页地址
    //根据nums总数，和prepage每页数量 生成分页总数
    totalpages := int(math.Ceil(float64(nums) / float64(prepage))) //page总数
    if page > totalpages {
        page = totalpages
    }
    if page <= 0 {
        page = 1
    }
    var pages []int
    switch {
    case page >= totalpages-5 && totalpages > 5: //最后5页
        start := totalpages - 5 + 1
        firstpage = page - 1
        lastpage = int(math.Min(float64(totalpages), float64(page+1)))
        pages = make([]int, 5)
        for i, _ := range pages {
            pages[i] = start + i
        }
    case page >= 3 && totalpages > 5:
        start := page - 3 + 1
        pages = make([]int, 5)
        firstpage = page - 3
        for i, _ := range pages {
            pages[i] = start + i
        }
        firstpage = page - 1
        lastpage = page + 1
    default:
        pages = make([]int, int(math.Min(5, float64(totalpages))))
        for i, _ := range pages {
            pages[i] = i + 1
        }
        firstpage = int(math.Max(float64(1), float64(page-1)))
        lastpage = page + 1
        //fmt.Println(pages)
    }
    paginatorMap := make(map[string]interface{})
    paginatorMap["pages"] = pages
    paginatorMap["totalpages"] = totalpages
    paginatorMap["firstpage"] = firstpage
    paginatorMap["lastpage"] = lastpage
    paginatorMap["currpage"] = page
    return paginatorMap
}

html页面

 <div class="am-cf">
  共{{.totals}}条记录 共记{{.paginator.totalpages}} 页 当前页  {{.paginator.currpage}}
  <div class="am-fr">
    <ul class="am-pagination">
    <li class=""><a href="/clubadmin/topics/{{.paginator.firstpage}}">«</a></li> 
    {{range $index,$page := .paginator.pages}}
      <li  {{if eq $.paginator.currpage $page }}class="am-active"{{end}}><a href="/clubadmin/topics/{{$page}}">{{$page}}</a></li>  
    {{end}}
      <li><a href="/clubadmin/topics/{{.paginator.lastpage}}">»</a></li>
    </ul>
  </div>
</div>

问题描述

使用两个 goroutine 交替打印序列，一个 goroutinue 打印数字， 另外一个goroutine打印字母， 最终效果如下 12AB34CD56EF78GH910IJ 。

解题思路

问题很简单，使用 channel 来控制打印的进度。使用两个 channel ，来分别控制数字和字母的打印序列， 数字打印完成后通过 channel 通知字母打印, 字母打印完成后通知数字打印，然后周而复始的工作。

实际编码

runtime.GOMAXPROCS(runtime.NumCPU())
chan_n := make(chan bool)
chan_c := make(chan bool, 1)
done := make(chan struct{})

go func() {
  for i := 1; i < 11; i += 2 {
    <-chan_c
    fmt.Print(i)
    fmt.Print(i + 1)
    chan_n <- true
  }
}()

go func() {
  char_seq := []string{"A","B","C","D","E","F","G","H","I","J","K"}
  for i := 0; i < 10; i += 2 {
    <-chan_n
    fmt.Print(char_seq[i])
    fmt.Print(char_seq[i+1])
    chan_c <- true
  }
  done <- struct{}{}
}()

chan_c <- true
<-done

代码执行结果:

12AB34CD56EF78GH910IJ

随机抽奖

问题描述

用户随机抽奖，数据结构如下所示：

// map中，key代表名称，value代表成交单数
var users map[string]int64 = map[string]int64{
  "a": 10,
  "b": 6,
  "c": 3,
  "d": 12,
  "f": 1,
}

解决思路

从map中选取随机用户，拿到这个编码问题，有点懵逼,但仔细一想，只需把关注用户的区间，转变一下数据结构即解题。 把map转成array，思考起来就简单多了，原有问题变成了从0至n-1中选取一个数字，数字对应的用户即中奖用户。

实际编码

package main

import (
  "fmt"
  "math/rand"
  "time"
)

func GetAwardUserName(users map[string]int64) (name string) {
  sizeOfUsers := len(users)
  award_index := rand.Intn(sizeOfUsers)

  var index int
  for u_name, _ := range users {
    if index == award_index {
      name = u_name
      return
    }
    index += 1
  }
  return
}

func main() {
  var users map[string]int64 = map[string]int64{
    "a": 10,
    "b": 6,
    "c": 3,
    "d": 12,
    "e": 20,
    "f": 1,
  }

  rand.Seed(time.Now().Unix())
  award_stat := make(map[string]int64)
  for i := 0; i < 1000; i += 1 {
    name := GetAwardUserName(users)
    if count, ok := award_stat[name]; ok {
      award_stat[name] = count + 1
    } else {
      award_stat[name] = 1
    }
  }

  for name, count := range award_stat {
    fmt.Printf("user: %s, award count: %d\n", name, count)
  }

  return
}

代码执行结果：

user: f, award count: 178
user: d, award count: 152
user: b, award count: 159
user: e, award count: 182
user: c, award count: 170
user: a, award count: 159

权重抽奖

问题描述

数据结构和上面一致，只是问题发生变化，需要更加用户的成单数来抽奖，用户成单越多，中奖概率越高，结构如下所示：

// map中，key代表名称，value代表成交单数
var users map[string]int64 = map[string]int64{
  "a": 10,
  "b": 6,
  "c": 3,
  "d": 12,
  "f": 1,
}

解决思路

这一题是上一题的延伸，加了订单数进去，做为权重来为用户抽奖。此题和上面的问题如此的相似，可把上面的问题， 理解成所有的用户权重都相同的抽奖，而此题是权重不同的抽奖。解决此问题，依旧是把map转为数组来思考， 把各用户的权重，从前到后依次拼接到数轴上，数轴的起点到终点即时中奖区间，而随机数落到的那个用户的区间，那个用户即为中奖用户。

实际编码

package main

import (
  "fmt"
  "math/rand"
  "time"
)

func GetAwardUserName(users map[string]int64) (name string) {
  type A_user struct {
    Name   string
    Offset int64
    Num    int64
  }

  a_user_arr := make([]*A_user, 0)
  var sum_num int64
  for name, num := range users {
    a_user := &A_user{
      Name:   name,
      Offset: sum_num,
      Num:    num,
    }
    a_user_arr = append(a_user_arr, a_user)
    sum_num += num
  }

  award_num := rand.Int63n(sum_num)

  for index, _ := range a_user_arr {
    a_user := a_user_arr[index]
    if a_user.Offset+a_user.Num > award_num {
      name = a_user.Name
      return
    }
  }
  return
}

func main() {
  var users map[string]int64 = map[string]int64{
    "a": 10,
    "b": 5,
    "c": 15,
    "d": 20,
    "e": 10,
    "f": 30,
  }

  rand.Seed(time.Now().Unix())
  award_stat := make(map[string]int64)
  for i := 0; i < 10000; i += 1 {
    name := GetAwardUserName(users)
    if count, ok := award_stat[name]; ok {
      award_stat[name] = count + 1
    } else {
      award_stat[name] = 1
    }
  }

  for name, count := range award_stat {
    fmt.Printf("user: %s, award count: %d\n", name, count)
  }

  return
}

代码执行结果：

user: c, award count: 1667
user: f, award count: 3310
user: e, award count: 1099
user: d, award count: 2276
user: b, award count: 549
user: a, award count: 1099