Go 中的并发：从基础知识到高级概念

go functionname()

go func() {
    // function body
}()

package main

import (
    "fmt"
    "time"
)

func printnumbers() {
    for i := 1; i <= 5; i++ {
        time.sleep(100 * time.millisecond)
        fmt.printf("%d ", i)
    }
}

func printletters() {
    for i := 'a'; i <= 'e'; i++ {
        time.sleep(150 * time.millisecond)
        fmt.printf("%c ", i)
    }
}

func main() {
    go printnumbers()
    go printletters()
    time.sleep(2 * time.second)
    fmt.println("\nmain function finished")
}

package main

import (
    "fmt"
    "time"
)

// printnumbers is a function that prints numbers from 1 to 5
// it will be run as a goroutine
func printnumbers() {
    for i := 1; i <= 5; i++ {
        time.sleep(500 * time.millisecond) // sleep for 500ms to simulate work
        fmt.printf("%d ", i)
    }
}

// printletters is a function that prints letters from 'a' to 'e'
// it will also be run as a goroutine
func printletters() {
    for i := 'a'; i <= 'e'; i++ {
        time.sleep(300 * time.millisecond) // sleep for 300ms to simulate work
        fmt.printf("%c ", i)
    }
}

func main() {
    // start printnumbers as a goroutine
    // the 'go' keyword before the function call creates a new goroutine
    go printnumbers()

    // start printletters as another goroutine
    go printletters()

    // sleep for 3 seconds to allow goroutines to finish
    // this is a simple way to wait, but not ideal for production code
    time.sleep(3 * time.second)

    // print a newline for better formatting
    fmt.println("\nmain function finished")
}

ch := make(chan int)  // unbuffered channel of integers

ch <- 42  // send the value 42 to the channel

value := <-ch  // receive a value from the channel

ch := make(chan int)
go func() {
    ch <- 42  // this will block until the value is received
}()
value := <-ch  // this will receive the value

ch := make(chan int, 2)
ch <- 1  // doesn't block
ch <- 2  // doesn't block
ch <- 3  // this will block until a value is received

func send(ch chan<- int) {
    ch <- 42
}

func receive(ch <-chan int) {
    value := <-ch
    fmt.println(value)
}

close(ch)

value, ok := <-ch
if !ok {
    fmt.println("channel is closed")
}

for value := range ch {
    fmt.Println(value)
}