1. 简介

1.1 什么是Go语言

高性能、高并发
语法简单、学习曲线平缓
丰富的标准款
完善的工具链
静态链接
快速编译
跨平台
垃圾回收

1.2 哪些公司在使用Go语言

1.3 字节跳动为什么全面拥抱Go语言

最初使用的Python，由于性能问题换成了Go
C++不太适合在线Web业务
早期剸断非Java背景
性能比较好
部署简单、学习成本低
内部RPC和HTTP框架的推广

2 开发环境

2.1 安装Golang

All releases - The Go Programming Language

Go下载 - Go语言中文网 - Golang中文社区 (studygolang.com)

七牛云 - Goproxy.cn

2.2 配置集成开发环境

3. 基础语法

3.1 Hello World

import "fmt"  
  
func main() {  
    fmt.Print("hello world")  
}

3.2 变量

package main

import (
    "fmt"
    "math"
)

func main() {
    var a = "initial"
    var b, c int = 1, 2
    var d = true
    var e float64
    f := float32(e)
    g := a + "foo"
    fmt.Println(a, b, c, d, e, f)
    fmt.Println(g)

    const s string = "constant"
    const h = 5000000
    const i = 3e20 / h
    fmt.Println(s, h, i, math.Sin(h), math.Sin(i))
}

3.3 if-else

package main

import "fmt"

func main() {
    if 7%2 == 0 {
        fmt.Println("7 is even")
    } else {
        fmt.Println("7 is odd")
    }

    if 8%4 == 0 {
        fmt.Println("8 is divisible by 4")
    }

    if num := 9; num < 0 {
        fmt.Println(num, "is negative")
    } else if num < 10 {
        fmt.Println(num, "has 1 digit")
    } else {
        fmt.Println(num, "has multiple digits")
    }
}

3.4 循环

package main

import "fmt"

func main() {
	i := 1
	for {
		fmt.Println("loop")
		break
	}

	for j := 7; i < 9; j++ {
		fmt.Println(j)
	}

	for n := 0; n < 5; n++ {
		if n%2 == 0 {
			continue
		}
		fmt.Println(n)
	}

	for i <= 3 {
		fmt.Println(i)
		i = i + 1
	}
}

3.5 switch

package main

import (
	"fmt"
	"time"
)

func main() {
	a := 2
	switch a {
	case 1:
		fmt.Println("one")
	case 2:
		fmt.Println("two")
	case 3:
		fmt.Println("three")
	case 4, 5:
		fmt.Println("four or five")
	default:
		fmt.Println("other")
	}

	t := time.Now()
	switch {
	case t.Hour() < 12:
		fmt.Println("It's before noon")
	default:
		fmt.Println("It's after noon")
	}
}

3.6 数组

package main

import "fmt"

func main() {
	var a [5]int
	a[4] = 100
	fmt.Println(a[4], len(a))

	b := [5]int{1, 2, 3, 4, 5}
	fmt.Println(b)

	var twoD [2][3]int
	for i := 0; i < 2; i++ {
		for j := 0; j < 3; j++ {
			twoD[i][j] = i + j
		}
	}
	fmt.Println("2d: ", twoD)
}

3.7 切片

package main

import "fmt"

func main() {
	s := make([]string, 3)
	s[0] = "a"
	s[1] = "b"
	s[2] = "c"
	fmt.Println("get", s[2])
	fmt.Println("len", len(s))

	s = append(s, "d")
	s = append(s, "e", "f")
	fmt.Println(s)

	c := make([]string, len(s))
	copy(c, s)
	fmt.Println(c)

	fmt.Println(s[2:5])
	fmt.Println(s[:5])
	fmt.Println(s[2:])

	good := []string{"g", "o", "o", "d"}
	fmt.Println(good)
}

3.8 map

package main

import "fmt"

func main() {
	m := make(map[string]int)
	m["one"] = 1
	m["two"] = 2
	fmt.Println(len(m))
	fmt.Println(m["one"])
	fmt.Println(m["unknow"])

	r, ok := m["unknow"]
	fmt.Println(r, ok)

	delete(m, "one")

	m2 := map[string]int{"one": 1, "two": 2}
	var m3 = map[string]int{"one": 1, "two": 2}
	fmt.Println(m2, m3)
}

3.9 range

package main

import (
	"fmt"
)

func main() {
	nums := []int{2, 3, 4}
	sum := 0
	for i, num := range nums {
		sum += num
		if num == 2 {
			fmt.Println("index:", i, "num:", num)
		}
	}
	fmt.Println(sum)

	m := map[string]string{"a": "A", "b": "B"}
	for k, v := range m {
		fmt.Println(k, v)
	}
	for k := range m {
		fmt.Println("key", k)
	}
}

3.10 函数

package main

import "fmt"

func add(a int, b int) int {
	return a + b
}

func add2(a, b int) int {
	return a + b
}

func exists(m map[string]string, k string) (v string, ok bool) {
	v, ok = m[k]
	return v, ok
}

func main() {
	res := add(1, 2)
	fmt.Println(res)

	v, ok := exists(map[string]string{"a": "A"}, "a")
	fmt.Println(v, ok)
}

3.11 指针

package main

import "fmt"

func add2(n int) {
	n += 2
}

func add2ptr(n *int) {
	*n += 2
}

func main() {
	n := 5
	add2(n)
	fmt.Println(n)
	add2ptr(&n)
	fmt.Println(n)
}

3.12 结构体

package main

import "fmt"

type user struct {
	name     string
	password string
}

func main() {
	a := user{name: "wang", password: "1024"}
	b := user{"wang", "1024"}
	c := user{name: "wang"}
	c.password = "1024"
	var d user
	d.name = "wang"
	d.password = "1024"

	fmt.Println(a, b, c, d)
	fmt.Println(checkPassword(a, "haha"))
	fmt.Println(checkPassword2(&a, "haha"))
}

func checkPassword(u user, password string) bool {
	return u.password == password
}

func checkPassword2(u *user, password string) bool {
	return u.password == password
}

3.13 结构体方法

package main

import "fmt"

type user struct {
	name     string
	password string
}

func (u user) checkPassword(password string) bool {
	return u.password == password
}

func (u *user) resetPassword(password string) {
	u.password = password
}

func main() {
	a := user{name: "wang", password: "1024"}
	a.resetPassword("2048")

	fmt.Println(a.checkPassword("2048"))
}

3.14 错误处理

package main

import (
	"errors"
	"fmt"
)

type user struct {
	name     string
	password string
}

func findUser(users []user, name string) (v *user, err error) {
	for _, u := range users {
		if u.name == name {
			return &u, nil
		}
	}
	return nil, errors.New("not found")
}

func main() {
	u, err := findUser([]user{{"wang", "1024"}}, "wang")
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(u.name)

	if u, err := findUser([]user{{"wang", "1024"}}, "li"); err != nil {
		fmt.Println(err)
		return
	} else {
		fmt.Println(u.name)
	}
}

3.15 字符串操作

package main

import (
	"fmt"
	"strings"
)

func main() {
	a := "hello"
	fmt.Println(strings.Contains(a, "ll"))
	fmt.Println(strings.Count(a, "l"))
	fmt.Println(strings.HasPrefix(a, "he"))
	fmt.Println(strings.HasSuffix(a, "llo"))
	fmt.Println(strings.Index(a, "ll"))
	fmt.Println(strings.Join([]string{"he", "llo"}, "-"))
	fmt.Println(strings.Repeat(a, 2))
	fmt.Println(strings.Replace(a, "e", "E", -1))
	fmt.Println(strings.Split("a-b-c", "-"))
	fmt.Println(strings.ToLower(a))
	fmt.Println(strings.ToUpper(a))
	fmt.Println(len(a))
	b := "你好"
	fmt.Println(len(b))
}

3. 16 字符串格式化

package main

import "fmt"

type point struct {
	x, y int
}

func main() {
	s := "hello"
	n := 123
	p := point{1, 2}
	fmt.Println(s, n)
	fmt.Println(p)

	fmt.Println("s=%v", s)
	fmt.Println("n=%v", n)
	fmt.Println("p=%v", p)
	fmt.Println("p=%+v", p)
	fmt.Println("p=%#v", p)

	f := 3.141592653
	fmt.Println(f)
	fmt.Println("%.2f", f)
}

3.17 JSON处理

package main

import (
	"encoding/json"
	"fmt"
)

type userInfo struct {
	Name  string
	Age   int `json:"age"`
	Hobby []string
}

func main() {
	a := userInfo{Name: "wang", Age: 18, Hobby: []string{"Golang", "TypeScript"}}
	buf, err := json.Marshal(a)
	if err != nil {
		panic(err)
	}
	fmt.Println(buf)
	fmt.Println(string(buf))

	buf, err = json.MarshalIndent(a, "", "\t")
	if err != nil {
		panic(err)
	}
	fmt.Println(string(buf))

	var b userInfo
	err = json.Unmarshal(buf, &b)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%#v\n", b)
}

3.18 时间处理

package main

import (
	"fmt"
	"time"
)

func main() {
	now := time.Now()
	fmt.Println(now)
	t := time.Date(2022, 3, 27, 1, 25, 16, 0, time.UTC)
	t2 := time.Date(2022, 3, 27, 2, 30, 36, 0, time.UTC)
	fmt.Println(t)
	fmt.Println(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute())
	fmt.Println(t.Format("2006-01-02 15:04:05"))
	diff := t2.Sub(t)
	fmt.Println(diff)
	fmt.Println(diff.Minutes(), diff.Seconds())
	t3, err := time.Parse("2006-01-02 15:04:05", "2022-03-27 01:25:36")
	if err != nil {
		panic(err)
	}
	fmt.Println(t3 == t)
	fmt.Println(now.Unix())
}

3.19 数字解析

package main

import (
	"fmt"
	"strconv"
)

func main() {
	f, _ := strconv.ParseFloat("1.234", 64)
	fmt.Println(f)

	n, _ := strconv.ParseInt("111", 10, 64)
	fmt.Println(n)

	n, _ = strconv.ParseInt("0x1000", 0, 64)
	fmt.Println(n)

	n2, _ := strconv.Atoi("123")
	fmt.Println(n2)

	n2, err := strconv.Atoi("AAA")
	fmt.Println(n2, err)
}

3. 20 进程信息

package main

import (
	"fmt"
	"os"
	"os/exec"
)

func main() {
	fmt.Println(os.Args)
	fmt.Println(os.Getenv("PATH"))
	fmt.Println(os.Setenv("AA", "BB"))

	buf, err := exec.Command("grep", "127.0.0.1", "/etc/host").CombinedOutput()
	if err != nil {
		panic(err)
	}
	fmt.Println(string(buf))
}

走近Go语言基础语法 | 青训营

1. 简介

1.1 什么是Go语言

1.2 哪些公司在使用Go语言

1.3 字节跳动为什么全面拥抱Go语言

2 开发环境

2.1 安装Golang

2.2 配置集成开发环境

3. 基础语法

3.1 Hello World

3.2 变量

3.3 if-else

3.4 循环

3.5 switch

3.6 数组

3.7 切片

3.8 map

3.9 range

3.10 函数

3.11 指针

3.12 结构体

3.13 结构体方法

3.14 错误处理

3.15 字符串操作

3. 16 字符串格式化

3.17 JSON处理

3.18 时间处理

3.19 数字解析

3. 20 进程信息