Go语言官网Example

2021-02-17 15:19

阅读：550

标签：sele cell 返回 str equal size creat cat unix

参考文档：https://gobyexample.com/

数组

package main

import "fmt"

func main() {

    var a [5]int
    fmt.Println("emp:", a)

    a[4] = 100
    fmt.Println("set:", a)
    fmt.Println("get:", a[4])

    fmt.Println("len:", len(a))

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

    var twoD [2][3]int
    for i := 0; i

切片

package main

import "fmt"

func main() {

    s := make([]string, 3)
    fmt.Println("emp:", s)

    s[0] = "a"
    s[1] = "b"
    s[2] = "c"
    fmt.Println("set:", s)
    fmt.Println("get:", s[2])

    fmt.Println("len:", len(s))

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

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

    l := s[2:5]
    fmt.Println("sl1:", l)

    l = s[:5]
    fmt.Println("sl2:", l)

    l = s[2:]
    fmt.Println("sl3:", l)

    t := []string{"g", "h", "i"}
    fmt.Println("dcl:", t)

    twoD := make([][]int, 3)
    for i := 0; i

字典

package main

import "fmt"

func main() {

    m := make(map[string]int)

    m["k1"] = 7
    m["k2"] = 13

    fmt.Println("map:", m)

    v1 := m["k1"]
    fmt.Println("v1: ", v1)

    fmt.Println("len:", len(m))

    delete(m, "k2")
    fmt.Println("map:", m)

    _, prs := m["k2"]
    fmt.Println("prs:", prs)

    n := map[string]int{"foo": 1, "bar": 2}
    fmt.Println("map:", n)
}

/*
map: map[k1:7 k2:13]
v1:  7
len: 2
map: map[k1:7]
prs: false
map: map[bar:2 foo:1]*/

遍历

package main

import "fmt"

func main() {

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

    for i, num := range nums {
        if num == 3 {
            fmt.Println("index:", i)
        }
    }

    kvs := map[string]string{"a": "apple", "b": "banana"}
    for k, v := range kvs {
        fmt.Printf("%s -> %s\n", k, v)
    }

    for k := range kvs {
        fmt.Println("key:", k)
    }

    for i, c := range "go" {
        fmt.Println(i, c)
    }
}

/*
sum: 9
index: 1
a -> apple
b -> banana
key: a
key: b
0 103
1 111*/

闭包

package main

import "fmt"

func intSeq() func() int {
    i := 0
    return func() int {
        i++
        return i
    }
}

func main() {

    nextInt := intSeq()

    fmt.Println(nextInt())
    fmt.Println(nextInt())
    fmt.Println(nextInt())

    newInts := intSeq()
    fmt.Println(newInts())
}

//1 2 3 1

递归

package main

import "fmt"

func fact(n int) int {
    if n == 0 {
        return 1
    }
    return n * fact(n-1)
}

func main() {
    fmt.Println(fact(7))
}

//5040

结构体

package main

import "fmt"

type person struct {
    name string
    age  int
}

func newPerson(name string) *person {

    p := person{name: name}
    p.age = 42
    return &p
}

func main() {

    fmt.Println(person{"Bob", 20})

    fmt.Println(person{name: "Alice", age: 30})

    fmt.Println(person{name: "Fred"})

    fmt.Println(&person{name: "Ann", age: 40})

    fmt.Println(newPerson("Jon"))

    s := person{name: "Sean", age: 50}
    fmt.Println(s.name)

    sp := &s
    fmt.Println(sp.age)

    sp.age = 51
    fmt.Println(sp.age)
}

/*{Bob 20}
{Alice 30}
{Fred 0}
&{Ann 40}
&{Jon 42}
Sean
50
51*/

结构体函数

package main

import "fmt"

type rect struct {
    width, height int
}

func (r *rect) area() int {
    return r.width * r.height
}

func (r rect) perim() int {
    return 2*r.width + 2*r.height
}

func main() {
    r := rect{width: 10, height: 5}

    fmt.Println("area: ", r.area())
    fmt.Println("perim:", r.perim())

    rp := &r
    fmt.Println("area: ", rp.area())
    fmt.Println("perim:", rp.perim())
}

/*area:  50
perim: 30
area:  50
perim: 30*/

接口

package main

import (
    "fmt"
    "math"
)

type geometry interface {
    area() float64
    perim() float64
}

type rect struct {
    width, height float64
}
type circle struct {
    radius float64
}

func (r rect) area() float64 {
    return r.width * r.height
}
func (r rect) perim() float64 {
    return 2*r.width + 2*r.height
}

func (c circle) area() float64 {
    return math.Pi * c.radius * c.radius
}
func (c circle) perim() float64 {
    return 2 * math.Pi * c.radius
}

func measure(g geometry) {
    fmt.Println(g)
    fmt.Println(g.area())
    fmt.Println(g.perim())
}

func main() {
    r := rect{width: 3, height: 4}
    c := circle{radius: 5}

    measure(r)
    measure(c)
}

/*
{3 4}
12
14
{5}
78.53981633974483
31.41592653589793*/

异常处理

package main

import (
    "errors"
    "fmt"
)

func f1(arg int) (int, error) {
    if arg == 42 {

        return -1, errors.New("can‘t work with 42")

    }

    return arg + 3, nil
}

type argError struct {
    arg  int
    prob string
}

func (e *argError) Error() string {
    return fmt.Sprintf("%d - %s", e.arg, e.prob)
}

func f2(arg int) (int, error) {
    if arg == 42 {

        return -1, &argError{arg, "can‘t work with it"}
    }
    return arg + 3, nil
}

func main() {

    for _, i := range []int{7, 42} {
        if r, e := f1(i); e != nil {
            fmt.Println("f1 failed:", e)
        } else {
            fmt.Println("f1 worked:", r)
        }
    }
    for _, i := range []int{7, 42} {
        if r, e := f2(i); e != nil {
            fmt.Println("f2 failed:", e)
        } else {
            fmt.Println("f2 worked:", r)
        }
    }

    _, e := f2(42)
    if ae, ok := e.(*argError); ok {
        fmt.Println(ae.arg)
        fmt.Println(ae.prob)
    }
}

/*f1 worked: 10
f1 failed: can‘t work with 42
f2 worked: 10
f2 failed: 42 - can‘t work with it
42
can‘t work with it*/

Channel同步

go语言提倡：非共享内存来同步数据，而是共享通信来同步数据

package main

import (
    "fmt"
    "time"
)

func worker(done chan bool) {
    fmt.Print("working...")
    time.Sleep(time.Second)
    fmt.Println("done")

    done

Select

Go’s select lets you wait on multiple channel operations. Combining goroutines and channels with select is a powerful feature of Go.

package main

import (
    "fmt"
    "time"
)

func main() {

    c1 := make(chan string)
    c2 := make(chan string)

    go func() {
        time.Sleep(1 * time.Second)
        c1

超时

package main

import (
    "fmt"
    "time"
)

func main() {

    c1 := make(chan string, 1)
    go func() {
        time.Sleep(2 * time.Second)
        c1

Channel的关闭和消费生产者模型

package main

import "fmt"

func main() {
    jobs := make(chan int, 5)
    done := make(chan bool)

    go func() {
        for {
            j, more :=

Channel的遍历

package main

import "fmt"

func main() {

    queue := make(chan string, 2)
    queue

Timer

package main
import (
	"fmt"
	"time"
)

func main() {
	timer1 := time.NewTimer(time.Second * 2)
	t1 := time.Now()
	fmt.Printf("t1:%v\n", t1)

	t2 :=

Timer.tickers

package main

import (
    "fmt"
    "time"
)

func main() {

    ticker := time.NewTicker(500 * time.Millisecond)
    done := make(chan bool)

    go func() {
        for {
            select {
            case

work pool

package main

import (
    "fmt"
    "time"
)

func worker(id int, jobs

WaitGroup

This is the function we’ll run in every goroutine. Note that a WaitGroup must be passed to functions by pointer.

package main

import (
    "fmt"
    "sync"
    "time"
)

func worker(id int, wg *sync.WaitGroup) {

    defer wg.Done()

    fmt.Printf("Worker %d starting\n", id)

    time.Sleep(time.Second)
    fmt.Printf("Worker %d done\n", id)
}

func main() {

    var wg sync.WaitGroup

    for i := 1; i

Rate Limiting

Rate limiting is an important mechanism for controlling resource utilization and maintaining quality of service. Go elegantly supports rate limiting with goroutines, channels, and tickers.

package main

import (
    "fmt"
    "time"
)

func main() {

    requests := make(chan int, 5)
    for i := 1; i

Atomic Counters

package main

import (
    "fmt"
    "sync"
    "sync/atomic"
)

func main() {

    var ops uint64

    var wg sync.WaitGroup

    for i := 0; i

Mutexs

In the previous example we saw how to manage simple counter state using atomic operations. For more complex state we can use a mutex to safely access data across multiple goroutines.

package main

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

func main() {

    var state = make(map[int]int)

    var mutex = &sync.Mutex{}

    var readOps uint64
    var writeOps uint64

    for r := 0; r

Stateful Goroutines 有状态的Goroutines

package main

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

type readOp struct {
    key  int
    resp chan int
}
type writeOp struct {
    key  int
    val  int
    resp chan bool
}

func main() {

    var readOps uint64
    var writeOps uint64

    reads := make(chan readOp)
    writes := make(chan writeOp)

    go func() {
        var state = make(map[int]int)
        for {
            select {
            case read :=

Collection Function

package main

import (
    "fmt"
    "strings"
)

func Index(vs []string, t string) int {
    for i, v := range vs {
        if v == t {
            return i
        }
    }
    return -1
}

func Include(vs []string, t string) bool {
    return Index(vs, t) >= 0
}

func Any(vs []string, f func(string) bool) bool {
    for _, v := range vs {
        if f(v) {
            return true
        }
    }
    return false
}

func All(vs []string, f func(string) bool) bool {
    for _, v := range vs {
        if !f(v) {
            return false
        }
    }
    return true
}

func Filter(vs []string, f func(string) bool) []string {
    vsf := make([]string, 0)
    for _, v := range vs {
        if f(v) {
            vsf = append(vsf, v)
        }
    }
    return vsf
}

func Map(vs []string, f func(string) string) []string {
    vsm := make([]string, len(vs))
    for i, v := range vs {
        vsm[i] = f(v)
    }
    return vsm
}

func main() {

    var strs = []string{"peach", "apple", "pear", "plum"}

    fmt.Println(Index(strs, "pear"))

    fmt.Println(Include(strs, "grape"))

    fmt.Println(Any(strs, func(v string) bool {
        return strings.HasPrefix(v, "p")
    }))

    fmt.Println(All(strs, func(v string) bool {
        return strings.HasPrefix(v, "p")
    }))

    fmt.Println(Filter(strs, func(v string) bool {
        return strings.Contains(v, "e")
    }))

    fmt.Println(Map(strs, strings.ToUpper))

}

/*
2
false
true
false
[peach apple pear]
[PEACH APPLE PEAR PLUM]*/

String Function

package main

import (
    "fmt"
    s "strings"
)

var p = fmt.Println

func main() {

    p("Contains:  ", s.Contains("test", "es"))
    p("Count:     ", s.Count("test", "t"))
    p("HasPrefix: ", s.HasPrefix("test", "te"))
    p("HasSuffix: ", s.HasSuffix("test", "st"))
    p("Index:     ", s.Index("test", "e"))
    p("Join:      ", s.Join([]string{"a", "b"}, "-"))
    p("Repeat:    ", s.Repeat("a", 5))
    p("Replace:   ", s.Replace("foo", "o", "0", -1))
    p("Replace:   ", s.Replace("foo", "o", "0", 1))
    p("Split:     ", s.Split("a-b-c-d-e", "-"))
    p("ToLower:   ", s.ToLower("TEST"))
    p("ToUpper:   ", s.ToUpper("test"))
    p()

    p("Len: ", len("hello"))
    p("Char:", "hello"[1])
}package main

import (
    "fmt"
    s "strings"
)

var p = fmt.Println

func main() {

    p("Contains:  ", s.Contains("test", "es"))
    p("Count:     ", s.Count("test", "t"))
    p("HasPrefix: ", s.HasPrefix("test", "te"))
    p("HasSuffix: ", s.HasSuffix("test", "st"))
    p("Index:     ", s.Index("test", "e"))
    p("Join:      ", s.Join([]string{"a", "b"}, "-"))
    p("Repeat:    ", s.Repeat("a", 5))
    p("Replace:   ", s.Replace("foo", "o", "0", -1))
    p("Replace:   ", s.Replace("foo", "o", "0", 1))
    p("Split:     ", s.Split("a-b-c-d-e", "-"))
    p("ToLower:   ", s.ToLower("TEST"))
    p("ToUpper:   ", s.ToUpper("test"))
    p()

    p("Len: ", len("hello"))
    p("Char:", "hello"[1])
}

/*
Contains:   true
Count:      2
HasPrefix:  true
HasSuffix:  true
Index:      1
Join:       a-b
Repeat:     aaaaa
Replace:    f00
Replace:    f0o
Split:      [a b c d e]
ToLower:    test
ToUpper:    TEST
Len:  5
Char: 101*/

String formatting

package main

import (
    "fmt"
    "os"
)

type point struct {
    x, y int
}

func main() {

    p := point{1, 2}
    fmt.Printf("%v\n", p)

    fmt.Printf("%+v\n", p)

    fmt.Printf("%#v\n", p)

    fmt.Printf("%T\n", p)

    fmt.Printf("%t\n", true)

    fmt.Printf("%d\n", 123)

    fmt.Printf("%b\n", 14)

    fmt.Printf("%c\n", 33)

    fmt.Printf("%x\n", 456)

    fmt.Printf("%f\n", 78.9)

    fmt.Printf("%e\n", 123400000.0)
    fmt.Printf("%E\n", 123400000.0)

    fmt.Printf("%s\n", "\"string\"")

    fmt.Printf("%q\n", "\"string\"")

    fmt.Printf("%x\n", "hex this")

    fmt.Printf("%p\n", &p)

    fmt.Printf("|%6d|%6d|\n", 12, 345)

    fmt.Printf("|%6.2f|%6.2f|\n", 1.2, 3.45)

    fmt.Printf("|%-6.2f|%-6.2f|\n", 1.2, 3.45)

    fmt.Printf("|%6s|%6s|\n", "foo", "b")

    fmt.Printf("|%-6s|%-6s|\n", "foo", "b")

    s := fmt.Sprintf("a %s", "string")
    fmt.Println(s)

    fmt.Fprintf(os.Stderr, "an %s\n", "error")
}

/*
{1 2}
{x:1 y:2}
main.point{x:1, y:2}
main.point
true
123
1110
!
1c8
78.900000
1.234000e+08
1.234000E+08
"string"
"\"string\""
6865782074686973
0x42135100
|    12|   345|
|  1.20|  3.45|
|1.20  |3.45  |
|   foo|     b|
|foo   |b     |
a string
an error*/

Regular Expressions

package main

import (
    "bytes"
    "fmt"
    "regexp"
)

func main() {

    match, _ := regexp.MatchString("p([a-z]+)ch", "peach")
    fmt.Println(match)

    r, _ := regexp.Compile("p([a-z]+)ch")

    fmt.Println(r.MatchString("peach"))

    fmt.Println(r.FindString("peach punch"))

    fmt.Println(r.FindStringIndex("peach punch"))

    fmt.Println(r.FindStringSubmatch("peach punch"))

    fmt.Println(r.FindStringSubmatchIndex("peach punch"))

    fmt.Println(r.FindAllString("peach punch pinch", -1))

    fmt.Println(r.FindAllStringSubmatchIndex(
        "peach punch pinch", -1))

    fmt.Println(r.FindAllString("peach punch pinch", 2))

    fmt.Println(r.Match([]byte("peach")))

    r = regexp.MustCompile("p([a-z]+)ch")
    fmt.Println(r)

    fmt.Println(r.ReplaceAllString("a peach", ""))

    in := []byte("a peach")
    out := r.ReplaceAllFunc(in, bytes.ToUpper)
    fmt.Println(string(out))
}

/*
true
true
peach
[0 5]
[peach ea]
[0 5 1 3]
[peach punch pinch]
[[0 5 1 3] [6 11 7 9] [12 17 13 15]]
[peach punch]
true
p([a-z]+)ch
a 
a PEACH*/

Json

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

type response1 struct {
    Page   int
    Fruits []string
}

type response2 struct {
    Page   int      `json:"page"`
    Fruits []string `json:"fruits"`
}

func main() {

    bolB, _ := json.Marshal(true)
    fmt.Println(string(bolB))

    intB, _ := json.Marshal(1)
    fmt.Println(string(intB))

    fltB, _ := json.Marshal(2.34)
    fmt.Println(string(fltB))

    strB, _ := json.Marshal("gopher")
    fmt.Println(string(strB))

    slcD := []string{"apple", "peach", "pear"}
    slcB, _ := json.Marshal(slcD)
    fmt.Println(string(slcB))

    mapD := map[string]int{"apple": 5, "lettuce": 7}
    mapB, _ := json.Marshal(mapD)
    fmt.Println(string(mapB))

    res1D := &response1{
        Page:   1,
        Fruits: []string{"apple", "peach", "pear"}}
    res1B, _ := json.Marshal(res1D)
    fmt.Println(string(res1B))

    res2D := &response2{
        Page:   1,
        Fruits: []string{"apple", "peach", "pear"}}
    res2B, _ := json.Marshal(res2D)
    fmt.Println(string(res2B))

    byt := []byte(`{"num":6.13,"strs":["a","b"]}`)

    var dat map[string]interface{}

    if err := json.Unmarshal(byt, &dat); err != nil {
        panic(err)
    }
    fmt.Println(dat)

    num := dat["num"].(float64)
    fmt.Println(num)

    strs := dat["strs"].([]interface{})
    str1 := strs[0].(string)
    fmt.Println(str1)

    str := `{"page": 1, "fruits": ["apple", "peach"]}`
    res := response2{}
    json.Unmarshal([]byte(str), &res)
    fmt.Println(res)
    fmt.Println(res.Fruits[0])

    enc := json.NewEncoder(os.Stdout)
    d := map[string]int{"apple": 5, "lettuce": 7}
    enc.Encode(d)
}

/*
true
1
2.34
"gopher"
["apple","peach","pear"]
{"apple":5,"lettuce":7}
{"Page":1,"Fruits":["apple","peach","pear"]}
{"page":1,"fruits":["apple","peach","pear"]}
map[num:6.13 strs:[a b]]
6.13
a
{1 [apple peach]}
apple
{"apple":5,"lettuce":7}*/

Time

package main

import (
    "fmt"
    "time"
)

func main() {
    p := fmt.Println

    now := time.Now()
    p(now)

    then := time.Date(
        2009, 11, 17, 20, 34, 58, 651387237, time.UTC)
    p(then)

    p(then.Year())
    p(then.Month())
    p(then.Day())
    p(then.Hour())
    p(then.Minute())
    p(then.Second())
    p(then.Nanosecond())
    p(then.Location())

    p(then.Weekday())

    p(then.Before(now))
    p(then.After(now))
    p(then.Equal(now))

    diff := now.Sub(then)
    p(diff)

    p(diff.Hours())
    p(diff.Minutes())
    p(diff.Seconds())
    p(diff.Nanoseconds())

    p(then.Add(diff))
    p(then.Add(-diff))
}

/*
2012-10-31 15:50:13.793654 +0000 UTC
2009-11-17 20:34:58.651387237 +0000 UTC
2009
November
17
20
34
58
651387237
UTC
Tuesday
true
false
false
25891h15m15.142266763s
25891.25420618521
1.5534752523711128e+06
9.320851514226677e+07
93208515142266763
2012-10-31 15:50:13.793654 +0000 UTC
2006-12-05 01:19:43.509120474 +0000 UTC*/

Time Formatting

package main

import (
    "fmt"
    "time"
)

func main() {
    p := fmt.Println

    t := time.Now()
    p(t.Format(time.RFC3339))

    t1, e := time.Parse(
        time.RFC3339,
        "2012-11-01T22:08:41+00:00")
    p(t1)

    p(t.Format("3:04PM"))
    p(t.Format("Mon Jan _2 15:04:05 2006"))
    p(t.Format("2006-01-02T15:04:05.999999-07:00"))
    form := "3 04 PM"
    t2, e := time.Parse(form, "8 41 PM")
    p(t2)

    fmt.Printf("%d-%02d-%02dT%02d:%02d:%02d-00:00\n",
        t.Year(), t.Month(), t.Day(),
        t.Hour(), t.Minute(), t.Second())

    ansic := "Mon Jan _2 15:04:05 2006"
    _, e = time.Parse(ansic, "8:41PM")
    p(e)
}

/*
2014-04-15T18:00:15-07:00
2012-11-01 22:08:41 +0000 +0000
6:00PM
Tue Apr 15 18:00:15 2014
2014-04-15T18:00:15.161182-07:00
0000-01-01 20:41:00 +0000 UTC
2014-04-15T18:00:15-00:00
parsing time "8:41PM" as "Mon Jan _2 15:04:05 2006": ...*/

random Numbers

package main

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

func main() {

    fmt.Print(rand.Intn(100), ",")
    fmt.Print(rand.Intn(100))
    fmt.Println()

    fmt.Println(rand.Float64())

    fmt.Print((rand.Float64()*5)+5, ",")
    fmt.Print((rand.Float64() * 5) + 5)
    fmt.Println()

    s1 := rand.NewSource(time.Now().UnixNano())
    r1 := rand.New(s1)

    fmt.Print(r1.Intn(100), ",")
    fmt.Print(r1.Intn(100))
    fmt.Println()

    s2 := rand.NewSource(42)
    r2 := rand.New(s2)
    fmt.Print(r2.Intn(100), ",")
    fmt.Print(r2.Intn(100))
    fmt.Println()
    s3 := rand.NewSource(42)
    r3 := rand.New(s3)
    fmt.Print(r3.Intn(100), ",")
    fmt.Print(r3.Intn(100))
}


/*
81,87
0.6645600532184904
7.123187485356329,8.434115364335547
0,28
5,87
5,87*/

Reading File

package main

import (
    "bufio"
    "fmt"
    "io"
    "io/ioutil"
    "os"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func main() {

    dat, err := ioutil.ReadFile("/tmp/dat")
    check(err)
    fmt.Print(string(dat))

    f, err := os.Open("/tmp/dat")
    check(err)

    b1 := make([]byte, 5)
    n1, err := f.Read(b1)
    check(err)
    fmt.Printf("%d bytes: %s\n", n1, string(b1[:n1]))

    o2, err := f.Seek(6, 0)
    check(err)
    b2 := make([]byte, 2)
    n2, err := f.Read(b2)
    check(err)
    fmt.Printf("%d bytes @ %d: ", n2, o2)
    fmt.Printf("%v\n", string(b2[:n2]))

    o3, err := f.Seek(6, 0)
    check(err)
    b3 := make([]byte, 2)
    n3, err := io.ReadAtLeast(f, b3, 2)
    check(err)
    fmt.Printf("%d bytes @ %d: %s\n", n3, o3, string(b3))

    _, err = f.Seek(0, 0)
    check(err)

    r4 := bufio.NewReader(f)
    b4, err := r4.Peek(5)
    check(err)
    fmt.Printf("5 bytes: %s\n", string(b4))

    f.Close()
}

/*
hello
go
5 bytes: hello
2 bytes @ 6: go
2 bytes @ 6: go
5 bytes: hello*/

Write File

package main

import (
    "bufio"
    "fmt"
    "io/ioutil"
    "os"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func main() {

    d1 := []byte("hello\ngo\n")
    err := ioutil.WriteFile("/tmp/dat1", d1, 0644)
    check(err)

    f, err := os.Create("/tmp/dat2")
    check(err)

    defer f.Close()

    d2 := []byte{115, 111, 109, 101, 10}
    n2, err := f.Write(d2)
    check(err)
    fmt.Printf("wrote %d bytes\n", n2)

    n3, err := f.WriteString("writes\n")
    check(err)
    fmt.Printf("wrote %d bytes\n", n3)

    f.Sync()

    w := bufio.NewWriter(f)
    n4, err := w.WriteString("buffered\n")
    check(err)
    fmt.Printf("wrote %d bytes\n", n4)

    w.Flush()

}

/*
$ cat /tmp/dat1
hello
go
$ cat /tmp/dat2
some
writes
buffered*/

Line Filters

package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

func main() {

    scanner := bufio.NewScanner(os.Stdin)

    for scanner.Scan() {

        ucl := strings.ToUpper(scanner.Text())

        fmt.Println(ucl)
    }

    if err := scanner.Err(); err != nil {
        fmt.Fprintln(os.Stderr, "error:", err)
        os.Exit(1)
    }
}

/*
$ echo ‘hello‘   > /tmp/lines
$ echo ‘filter‘ >> /tmp/lines
cat /tmp/lines | go run line-filters.go
HELLO
FILTER*/

File Path

package main

import (
    "fmt"
    "path/filepath"
    "strings"
)

func main() {

    p := filepath.Join("dir1", "dir2", "filename")
    fmt.Println("p:", p)

    fmt.Println(filepath.Join("dir1//", "filename"))
    fmt.Println(filepath.Join("dir1/../dir1", "filename"))

    fmt.Println("Dir(p):", filepath.Dir(p))
    fmt.Println("Base(p):", filepath.Base(p))

    fmt.Println(filepath.IsAbs("dir/file"))
    fmt.Println(filepath.IsAbs("/dir/file"))

    filename := "config.json"

    ext := filepath.Ext(filename)
    fmt.Println(ext)

    fmt.Println(strings.TrimSuffix(filename, ext))

    rel, err := filepath.Rel("a/b", "a/b/t/file")
    if err != nil {
        panic(err)
    }
    fmt.Println(rel)

    rel, err = filepath.Rel("a/b", "a/c/t/file")
    if err != nil {
        panic(err)
    }
    fmt.Println(rel)
}

/*
p: dir1/dir2/filename
dir1/filename
dir1/filename
Dir(p): dir1/dir2
Base(p): filename
false
true
.json
config
t/file
../c/t/file*/

Context

In the previous example we looked at setting up a simple HTTP server. HTTP servers are useful for demonstrating the usage of context.Context for controlling cancellation. A Context carries deadlines, cancellation signals, and other request-scoped values across API boundaries and goroutines.


　package main

import (
    "fmt"
    "net/http"
    "time"
)

func hello(w http.ResponseWriter, req *http.Request) {

    ctx := req.Context()
    fmt.Println("server: hello handler started")
    defer fmt.Println("server: hello handler ended")

    select {
    case

Go语言官网Example

标签：sele cell 返回 str equal size creat cat unix

原文地址：https://www.cnblogs.com/double-W/p/12696026.html

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Go语言官网Example

数组

切片

字典

遍历

闭包

递归

结构体

结构体函数

接口

异常处理

Channel同步

Select

超时

Channel的关闭和消费生产者模型

Channel的遍历

Timer

Timer.tickers

work pool

WaitGroup

Rate Limiting

Atomic Counters

Mutexs

Stateful Goroutines 有状态的Goroutines

Collection Function

String Function

String formatting

Regular Expressions

Json

Time

Time Formatting

random Numbers

Reading File

Write File

Line Filters

File Path

Context

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