Channel

Introduction

A channel is a conduit for end-to-end data communication, often used for data sharing between goroutines.

Creating a channel

We use make to create a channel

ch1 := make(chan T) // Unbuffered

ch2 := make(chan T, 2) // Buffered

T is the data type.

Warning

• An unbuffered channel will be blocked until the data is received
• A buffered channel will be blocked when the sent data reaches the buffer size

Sending and receiving data

Using <- pointing to the channel means sending data to that channel, such as ch <- 10

Using <- on the left side of the channel means receiving data, such as <-ch

Closing a channel

Use close() to close a channel

close(ch)

Warning

• If you send a message to a channel that has already been close(), it will cause a panic

• Reading from a closed channel can get a zero value, if using range to read channel, then close will terminate the loop

We can use val, ok := <- ch to determine whether it is a zero value, if ok is false then the channel is already close

Select

We usually use select to receive channel data, you can also use default to set the default action, select can receive multiple channel at the same time, if multiple channel send data at the same time, it will randomly select a channel to complete the operation

select {
    case <-ch1:  // Receive ch1 data
        fmt.Println("ch1")  
    case <-ch2: // Receive ch2 data
        fmt.Println("ch2")
    case val := <-ch3:
        fmt.Println(ch3) //Receive ch3 data and print
    default:
        fmt.Println("default")
}

Example

The timer is implemented through channel to return the timing result

package main

import (
	"fmt"
	"time"
)

func main() {
	t := time.NewTicker(3*time.Second)
	fmt.Println("start")
	<-t.C
	fmt.Println("finish")
}

Precautions

• When using channel, be aware that there must be a data receiving end to avoid deadlock problems