Golang (2) - 码厩

#92 Golang 程序中内嵌 Lua

Golang 2023-04-19

package main

import (
    "fmt"
    "github.com/Shopify/go-lua"
)

func main() {
    state := lua.NewState()
    defer state.Close()

    // 加载 Lua 代码
    lua.DoString(state, `
        function add(a, b)
            return a + b
        end
    `)

    // 调用 Lua 函数
    lua.GetGlobal(state, "add")
    lua.PushInteger(state, 1)
    lua.PushInteger(state, 2)
    lua.Call(state, 2, 1)

    // 获取 Lua 函数返回值
    result := lua.ToInteger(state, -1)
    lua.Pop(state, 1)

    fmt.Println(result)
}

#91 Golang 多版本方案

Golang 2023-03-09

Ubuntu 更新源中的是 Go 1.18（apt install golang），现在 Go 1.20 出来了，我想尝尝鲜，就需要考虑多版本共存的方案了。

Python 有 pyenv，Node 有 nvm。
Go 也有一些社区项目，比如 syndbg/goenv stars 和 moovweb/gvm stars ，还有 owenthereal/goup stars 。

其中 gvm 之前有尝试过，参考：gvm: Golang 版本管理

本文是介绍官方的 dl，可以说是非常简单。

go install golang.org/dl/go1.20@latest

~/go/bin/go1.20 download
Downloaded   0.0% (   16384 / 99869470 bytes) ...
Downloaded   3.5% ( 3522544 / 99869470 bytes) ...
Downloaded   9.8% ( 9748480 / 99869470 bytes) ...
Downloaded  15.7% (15712240 / 99869470 bytes) ...
Downloaded  21.7% (21626880 / 99869470 bytes) ...
Downloaded  27.6% (27541296 / 99869470 bytes) ...
Downloaded  32.9% (32866288 / 99869470 bytes) ...
Downloaded  38.9% (38846464 / 99869470 bytes) ...
Downloaded  44.9% (44793840 / 99869470 bytes) ...
Downloaded  50.8% (50741248 / 99869470 bytes) ...
Downloaded  56.7% (56672240 / 99869470 bytes) ...
Downloaded  62.7% (62586864 / 99869470 bytes) ...
Downloaded  68.1% (67993600 / 99869470 bytes) ...
Downloaded  74.0% (73924304 / 99869470 bytes) ...
Downloaded  79.9% (79839200 / 99869470 bytes) ...
Downloaded  85.9% (85753856 / 99869470 bytes) ...
Downloaded  91.8% (91717424 / 99869470 bytes) ...
Downloaded  97.2% (97025728 / 99869470 bytes) ...
Downloaded 100.0% (99869470 / 99869470 bytes)
Unpacking /home/markjour/sdk/go1.20/go1.20.linux-amd64.tar.gz ...
Success. You may now run 'go1.20'

~/go/bin/go1.20 download
go1.20: already downloaded in /home/markjour/sdk/go1.20

~/sdk/go1.20/bin/go version
go version go1.20 linux/amd64

# sudo ln -sf ~/sdk/go1.20/bin/go /usr/local/bin/go
ln -sf ~/sdk/go1.20/bin/go ~/.local/bin/go1.20
ln -sf go1.20 ~/.local/bin/go

#90 《企业级 Go 项目开发实战》目录

Golang 2023-02-27

主要是参考一下这个目录，对照着查漏补缺。

#89 Golang 变量初始化顺序问题

Golang 2022-12-15

f1.go

package main

var A int = 3
var B int = A + 1
var C int = A

f2.go

package main

import "fmt"

var D = f()

func f() int {
    A = 1
    return 1
}

func main() {
    fmt.Println(A, B, C)
}

执行

markjour@victus ~/test02
$ go version
go version go1.18.6 windows/amd64

markjour@victus ~/test02
$ go run f1.go f2.go
1 4 3

markjour@victus ~/test02
$ go run f2.go f1.go
1 2 3

分析

f1f2 的情况下：变量初始化的顺序应该为 A B C D，所以输出 1 4 3 是没有问题的。
f2f1 的情况下：变量初始化的顺序应该为 A D B C，所以按理应该输出 1 2 1，实际确实输出 1 2 3。

f1 中 A C 中只要一个的初始化改成这样就可以符合预期：

func initA() int {
    return 3
}

func initC() int {
    return A
}

这是 Go 的一个 BUG，即将在 Go 1.20 修复。
知道就行了。

参考资料与拓展阅读

知乎，陈煎鱼, Go1.20 将会修改全局变量的初始化顺序。梅开二度，继续打破 Go1 兼容性承诺！
cmd/compile: global variable initialization done in unexpected order #51913
The Go Programming Language Specification, Package initialization

#88 Go DNS 解析

Golang DNS 2022-10-30

A 记录

package main

import (
    "fmt"
    "net"
)

func main() {
    // 方法 1
    // func ResolveIPAddr(network, address string) (*IPAddr, error)
    ipAddr, err := net.ResolveIPAddr("ip", "www.google.com")
    if err != nil {
        fmt.Println("解析IP地址失败:", err)

    } else {
        fmt.Println("IP地址是:", ipAddr.IP)
    }

    // 方法 2
    // func LookupMX(name string) ([]*MX, error)
    // func LookupTXT(name string) ([]string, error)
    // func LookupIP(host string) ([]IP, error)
    // func LookupHost(host string) ([]string, error) // only IPv4
    ips, err := net.LookupHost("www.google.com")
    if err != nil {
        fmt.Println("解析主机名失败:", err)
    } else {
        for _, ip := range ips {
            fmt.Println("IP地址是:", ip)
        }
    }
}

MX 记录

package main

import (
    "fmt"
    "net"
)

func main() {
    records, err := net.LookupMX("qq.com")
    if err != nil {
        fmt.Println("解析MX记录失败:", err)
    } else {
        fmt.Printf("%#v", records)
    }
}

指定 DNS 服务器

func queryMX(dns string, domain string) ([]*net.MX, error) {
    resolver := &net.Resolver{
        PreferGo: true,
        Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
            dialer := &net.Dialer{}
            return dialer.DialContext(ctx, "udp", dns)
        },
    }
    return resolver.LookupMX(context.Background(), domain)
}

完整版本

package main

import (
    "context"
    "fmt"
    "net"
    "strings"
    "time"
)

var dnsServers = []string{
    "223.5.5.5:53",
    "114.114.114.114:53",
    "8.8.8.8:53",
}

type IPType int

const (
    NotIP IPType = iota
    IPv4
    IPv6
)

const (
    DNSLookupTimeout = 500 * time.Millisecond // time.Duration
)

func GetIPType(host string) IPType {
    ip := net.ParseIP(host)
    if ip == nil {
        return NotIP
    }
    if ip.To4() != nil {
        return IPv4
    }
    if ip.To16() != nil {
        return IPv6
    }
    return NotIP
}

type Resolver struct {
    DNS      string
    Resolver *net.Resolver
}

func NewResolver(dns string) Resolver {
    resolver := Resolver{}
    resolver.DNS = dns
    resolver.Resolver = &net.Resolver{
        PreferGo: true,
        Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
            dialer := &net.Dialer{}
            return dialer.DialContext(ctx, "udp", dns)
        },
    }
    return resolver
}

func (r Resolver) QueryA(domain string) ([]string, error) {
    return r.Resolver.LookupHost(context.Background(), domain)
}

func (r Resolver) QueryMX(domain string) ([]*net.MX, error) {
    ctx, cancel := context.WithTimeout(context.Background(), DNSLookupTimeout)
    defer cancel()
    return r.Resolver.LookupMX(ctx, domain)
}

func (r Resolver) Query(domain string) ([]*net.MX, error) {
    addrs, err := r.QueryMX(domain)
    if err != nil {
        return nil, err
    }
    var result []*net.MX
    for _, addr := range addrs {
        // hostname := strings.TrimRight(addr.Host, ".")
        ipType := GetIPType(addr.Host)
        fmt.Printf("%s: %#v\n", addr.Host, ipType)
        if ipType == NotIP {
            ips, err := r.QueryA(addr.Host)
            if err != nil {
                continue
            }
            for _, ip := range ips {
                result = append(result, &net.MX{Host: ip, Pref: addr.Pref})
            }
        }
    }
    return result, nil
}

var resolvers map[string]Resolver

func Query(domain string) ([]*net.MX, error) {
    var addrs []*net.MX
    var err error
    for _, dns := range dnsServers {
        var r Resolver
        if r, ok := resolvers[dns]; !ok {
            r = NewResolver(dns)
            resolvers[dns] = r
        }
        addrs, err = r.Query(domain)
        if err == nil {
            break
        }
        fmt.Printf("Error: %s: %s: %#v\n", dns, domain, err)
    }
    return addrs, err
}

func QueryAsync(domain string, ch chan<- []*net.MX, errCh chan<- error) {
    addrs, err := Query(domain)
    if err != nil {
        errCh <- err
        return
    }
    ch <- addrs
}

func init() {
    resolvers = make(map[string]Resolver)
}

func main() {
    {
        domains := []string{"qq.com", "gmail.com", "google.com"}
        for _, domain := range domains {
            fmt.Println(strings.Repeat("=", 100))
            addrs, err := Query(domain)
            if err != nil {
                fmt.Printf("Error: %#v\n", err)
            } else {
                for _, addr := range addrs {
                    fmt.Printf("%#v\n", addr)
                }
            }
        }
    }

    {
        fmt.Println(strings.Repeat("=", 100))
        ch := make(chan []*net.MX)
        errCh := make(chan error)
        go QueryAsync("google.com", ch, errCh)
        select {
        case addrs := <-ch:
            fmt.Println("MX Records:")
            for _, addr := range addrs {
                fmt.Printf("%#v\n", addr)
            }
        case err := <-errCh:
            fmt.Println("Error:", err)
        }
    }
}

#87 gob：Golang 二进制编码格式（标准库）

Golang 2022-10-01

package main

import (
    "bytes"
    "encoding/gob"
    "fmt"
)

type Person struct {
    Name string
    Age  int
}

func main() {
    // 编码
    var buf bytes.Buffer
    enc := gob.NewEncoder(&buf)
    err := enc.Encode(Person{"John", 30})
    if err != nil {
        panic(err)
    }

    // 解码
    dec := gob.NewDecoder(&buf)
    var p Person
    err = dec.Decode(&p)
    if err != nil {
        panic(err)
    }

    fmt.Println(p)
}

#86 Golang 源码结构

Golang 2022-09-16

# tree -L 1 -d .
.
├── api
├── doc
├── lib
├── misc
├── src
└── test

6 directories

# tree -L 1 -d src/
src/
├── archive
├── bufio
├── builtin
├── bytes
├── cmd
├── compress
├── container
├── context
├── crypto
├── database
├── debug
├── embed
├── encoding
├── errors
├── expvar
├── flag
├── fmt
├── go
├── hash
├── html
├── image
├── index
├── internal
├── io
├── log
├── math
├── mime
├── net
├── os
├── path
├── plugin
├── reflect
├── regexp
├── runtime
├── sort
├── strconv
├── strings
├── sync
├── syscall
├── testdata
├── testing
├── text
├── time
├── unicode
├── unsafe
└── vendor

46 directories

tree -L 2 -d src/net/
src/net/
├── http
│   ├── cgi
│   ├── cookiejar
│   ├── fcgi
│   ├── httptest
│   ├── httptrace
│   ├── httputil
│   ├── internal
│   ├── pprof
│   └── testdata
├── internal
│   └── socktest
├── mail
├── rpc
│   └── jsonrpc
├── smtp
├── testdata
├── textproto
└── url

19 directories

#85 Golang UUID

Golang 2022-09-13

awesome-go 上面列出来的项目：

jakehl/goid - Generate and Parse RFC4122 compliant V4 UUIDs.
twharmon/gouid - Generate cryptographically secure random string IDs with just one allocation.
aidarkhanov/nanoid - A tiny and efficient Go unique string ID generator.
muyo/sno - Compact, sortable and fast unique IDs with embedded metadata.
oklog/ulid - Go implementation of ULID (Universally Unique Lexicographically Sortable Identifier).
uniq - No hassle safe, fast unique identifiers with commands.
agext/uuid - Generate, encode, and decode UUIDs v1 with fast or cryptographic-quality random node identifier.
gofrs/uuid - Implementation of Universally Unique Identifier (UUID). Supports both creation and parsing of UUIDs. Actively maintained fork of satori uuid.
google/uuid - Go package for UUIDs based on RFC 4122 and DCE 1.1: Authentication and Security Services.
edwingeng/wuid - An extremely fast globally unique number generator.
rs/xid - Xid is a globally unique id generator library, ready to be safely used directly in your server code.

我自己又在 GitHub 上搜罗了几个：

lithammer/shortuuid - 🍄 A generator library for concise, unambiguous and URL-safe UUIDs
jetpack-io/typeid - Type-safe, K-sortable, globally unique identifier inspired by Stripe IDs
satori/go.uuid - UUID package for Go
segmentio/ksuid - K-Sortable Globally Unique IDs

package main

import (
    "os/exec"

    guuid "github.com/google/uuid"
    suuid "github.com/satori/go.uuid"
)

func UseGoogle() string {
    id := guuid.New()
    return id.String()
}

func UseSatori() string {
    id := suuid.NewV4()
    return id.String()
}

func UseUuidgen() string {
    id, _ := exec.Command("uuidgen").Output()
    return string(id)
}

func main() {
    fmt.Println("Google UUID:", UseGoogle())
    fmt.Println("Satori UUID:", UseSatori())
    fmt.Println("Uuidgen UUID:", UseUuidgen())
}

#84 Go 谚语

Golang 2022-09-13

得知了 Go 谚语这么个东西，搜索一番，找到：

https://go-proverbs.github.io/
https://github.com/jboursiquot/go-proverbs
https://www.youtube.com/watch?v=PAAkCSZUG1c

原来是类似 Python 之禅（import this）一样的东西。

Don't communicate by sharing memory, share memory by communicating. 别通过共享内存通信，要通过通信共享内存。
Concurrency is not parallelism. 并发不是并行。
Channels orchestrate; mutexes serialize.
The bigger the interface, the weaker the abstraction. 接口越大, 抽象越弱。
Make the zero value useful.
interface{} says nothing.
Gofmt's style is no one's favorite, yet gofmt is everyone's favorite. 别争论风格问题，不管喜不喜欢，用 gofmt 就是了。
A little copying is better than a little dependency. 少量的复制好过引入新的依赖。
Syscall must always be guarded with build tags.
Cgo must always be guarded with build tags.
Cgo is not Go. 别用 cgo。
With the unsafe package there are no guarantees. 慎用 unsafe 包（安全无保障）
Clear is better than clever. 清晰的代码比聪明的代码好。
Reflection is never clear. 慎用反射（代码不清晰）。
Errors are values.
Don't just check errors, handle them gracefully.
Design the architecture, name the components, document the details.
Documentation is for users. 文档是给用户的（注意代码本身的可读性）。
Don't panic. 不要滥用 panic。

#83 Viper: Go 项目配置管理

Golang Viper 2022-07-22

main.go：

package main

import (
    "fmt"
    "os"

    "github.com/spf13/pflag"
    "github.com/spf13/viper"
)

func main() {
    // 1. 设置 Viper 配置
    viper.SetConfigName("config") // 配置文件名（不带后缀）
    viper.AddConfigPath(".")      // 配置文件路径
    viper.SetConfigType("yaml")   // 配置文件类型
    viper.AutomaticEnv()          // 自动读取环境变量

    // 2. 设置命令行参数
    pflag.String("name", "", "project name")
    pflag.String("host", "", "host address")
    pflag.String("port", "", "port number")
    pflag.String("config", "./config.yaml", "config file") // 配置文件参数
    pflag.Parse()
    viper.BindPFlags(pflag.CommandLine) // 将命令行参数绑定到 Viper

    // 3. 读取配置文件
    if configFile := viper.GetString("config"); configFile != "" {
        fmt.Println(configFile)
        if err := viper.ReadInConfig(); err != nil {
            fmt.Fprintf(os.Stderr, "读取配置文件失败：%v\n", err)
            os.Exit(1)
        }
    }

    // 4. 读取配置项
    projectName := viper.GetString("name")
    port := viper.GetInt("port")
    fmt.Printf("ProjectName: %s, Port: %d\n", projectName, port)
}

config.yaml：

name: hello
host: 10.10.0.172
port: 9090

支持环境变量、命令行参数、配置文件。
支持多种配置文件，包括 JSON，YAML，TOML，INI 等。
支持监控配置文件的变化，会自动加载新的配置。
支持从远程加载配置，比如 etcd、zk、consul、redis 等，
也可以通过 RemoteProvider 接口自定义远程数据源：

type RemoteProvider interface {
    Set(key string, value []byte) error
    Watch(key string) (chan *RemoteResponse, chan error)
    Get(key string) ([]byte, error)
}

支持默认值。

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