How to do concurrency in golang

Golang is an efficient, fast, and highly secure language, and its concurrency features make it an increasingly popular and powerful tool. This article starts with basic concepts and introduces how Golang implements concurrency.

1. Concurrency and Parallelism

The first thing that needs to be clarified is the difference between concurrency and parallelism. Concurrency refers to multiple tasks overlapping and running in the same time period, while parallelism refers to multiple tasks running at the same time. In practice, we often confuse the two, but in theory, they are completely different concepts.

2. Golang’s goroutine

Golang’s concurrency mainly depends on goroutine. Goroutine is a lightweight thread in Golang, started by the go keyword. The biggest difference between goroutine and threads is that it does not rely on operating system threads for execution, but is directly managed by Golang's runtime system. Each goroutine is an independent unit scheduled by the Go language runtime environment (runtime). They will run in a logical processor. The logical processor determines the allocation of goroutine to the actual number of threads in the operating system.

In Golang programs, the main function runs in a goroutine by default, and other goroutines can be started at any time and can be executed concurrently with the main function or other goroutines.

3. Use the go keyword to start goroutine

Use the go keyword to easily start goroutine. We only need to add the keyword go before the function call, and the system will automatically open a new goroutine as needed. For example:

go func1(arg1, arg2)

This statement will run the func1 function in the form of goroutine, and the synchronization code will continue to execute. At this time, the program will print out this statement first and then execute the following code immediately. At a certain time, the Go language runtime will start a new goroutine to run the function. In this case, we cannot directly know when the goroutine is started and when it ends.

For functions with return values, we need to wait for the goroutine to finish executing before proceeding to the next step. This process can be achieved by using channels.

4. Channel

Channel is a very important communication mechanism in Golang concurrent programming. Channels enable data exchange between goroutines. Channels always have send and receive operations, which by default block until the other end is ready.

The syntax for creating a channel is as follows:

channel := make(chan type)

where type can be any type, and channel is a pipe with type type.

The syntax for sending data to the channel is as follows:

channel <- data

This statement will send data to the channel and send it to the goroutine waiting to receive the data.

The syntax for receiving data from the channel in goroutine is as follows:

data := <- channel

This statement will receive data from the channel. If there is no data in the channel, this statement will block waiting for data to arrive.

Through channels, we can control the synchronization and concurrency between goroutines. For example:

ch := make(chan int)
go func(){
    ch <- 1
}()
data := <- ch

This statement will wait for the goroutine to send data to the channel after starting a new goroutine, and then receive data from the channel to continue execution.

5. Sync package

In addition to channels, Golang also provides a Sync package to support concurrent programming. This package provides many atomic operation functions and mechanisms such as mutex locks.

The atomic operation function is a very important concept in Golang concurrent programming. It can ensure that a series of operations are indivisible during execution. That is to say, other goroutines cannot see the intermediate state when performing atomic operations. , the object is either not modified or modified. This can solve the synchronization problem very well.

For example:

var sum int64 = 0
for i := 0; i < 10000; i++ {
    go func(){
        atomic.AddInt64(&sum, 1)
    }()
}

This statement demonstrates the use of atomic operation functions for calculation. In this program, the goroutine will continuously add 1 to the sum variable without creating race conditions. This problem caused by the lack of synchronization of reading and writing variables is called a race condition, and atomic operation functions can perfectly avoid this problem.

6. Summary

This article introduces how Golang implements concurrency. It mainly talks about basic elements such as Golang's goroutine, channels, and atomic operations in the Sync package, as well as their application in concurrent programming. Golang's concurrency features not only help in many fields such as engineering task processing, server concurrent processing, and real-time system development, but are also one of the important reasons why Golang has become a popular programming language.

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