How to close channel in golang

Golang is a popular and efficient programming language, and its concurrency feature is one of the biggest features of the language. In Golang, a channel is an important concurrency primitive. It is an object that can pass data between two or more goroutines. When using channels, closing the channel is a common operation. This article will explore the methods of closing channels in Golang and some precautions.

1. Why do you need to close the channel?

The closing of the channel indicates that the channel will no longer accept more data, so that the goroutine that reads data from the channel can be notified and exit the waiting state without blocking. Closing the channel can also avoid wasting resources caused by goroutine waiting to receive data.

Of course, not all channels need to be closed. It is reasonable to close the channel only under the following circumstances:

1. When the sender has finished sending the data and there is no more data to send, close the channel. This way the receiver can be notified and does not have to wait for the data to arrive.
2. When the receiver reads data from the channel and has received the exit signal, the channel can be closed. This way the sender can be notified without having to send data all the time.

2. How to close the channel?

In Golang, we can use the built-in function close to close the channel.

close(ch)

Among them, ch is the channel that needs to be closed. When we no longer need to pass any value to the channel, we can call close(ch) to close the channel. Note that only the sender can close the channel. For the receiver, it can only judge whether the channel is closed by the Boolean value returned by the channel.

In order to ensure normal concurrent operations, select multiplexing can be used to close the channel. The specific method is as follows:

func closeChan(ch chan int, done chan bool) {

<-done //等待接收信号
close(ch)

}

func main() {

ch := make(chan int)
done := make(chan bool)
go closeChan(ch, done)
//此处可以往通道ch中发送数据
//等发送完成后，发送一个退出信号
done <- true

}

In the above code, the done channel in the closeChan function is the channel for controlling the signal. When the program needs to close the channel, we only need to send an exit signal instead of calling close(ch) directly. In the go coroutine, the closeChan(ch, done) function is executed. When the exit signal of the done channel is received, close(ch) is executed to close the channel.

3. Precautions

1. If there is no need to close the channel, do not force the channel to be closed. After closing the channel, values ​​can no longer be sent to the channel, but we lack the ability to control the channel, and the possibility of data competition will increase.
2. After calling close(ch), all unread data will be discarded, so be careful when reading channel data.
3. After closing the channel, trying to send data to the channel will generate a runtime error. So before sending data, make sure the channel is not closed.

4. Summary

Close the channel is one of the more common operations in Golang, which can help us better control the concurrency between goroutines. When using channels, we need to think carefully about when to close the channel and how to close the channel correctly. Through the above explanation, I believe that everyone will become more proficient in using Golang channels, and at the same time, they can avoid some problems caused by improper use of channels.

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