Will the main function of go language wait?

Yes, in most cases, the main function will wait for other goroutines to complete. When the main function executes to the last line of code, if there are other goroutines running, the main function will wait for these goroutines to finish executing before exiting. . This is because in the concurrency model of the Go language, the main function will wait for all goroutines to complete before exiting to ensure the correct execution of the program. In Go language, you can use "sync.WaitGroup" to implement the main function waiting for other goroutines to complete.

The operating environment of this article: Windows 10 system, Go1.20.4 version, Dell G3 computer.

The main function of Go language is the entry point of every Go program, and it is the starting point of program execution. The main function is called when the program starts and exits automatically when the program ends. However, whether the main function waits for other goroutines to complete depends on the specific code implementation.

In most cases, the main function will wait for other goroutines to complete. When the main function executes the last line of code, if there are other goroutines running, the main function will wait for these goroutines to finish executing before exiting. This is because in the concurrency model of the Go language, the main function will wait for all goroutines to complete before exiting to ensure the correct execution of the program.

However, there are some cases where the main function may not wait for other goroutines to complete. For example, if the `os.Exit()` function is used in the main function to exit the program, the main function will terminate immediately and will not wait for other goroutines to complete. In addition, if the `runtime.Goexit()` function is used in the main function to exit the current goroutine, the main function will also terminate immediately and will not wait for other goroutines to complete.

In the Go language, we can use `sync.WaitGroup` to implement the function of the main function waiting for other goroutines to complete. `sync.WaitGroup` is a counting semaphore used to wait for a group of goroutines to complete. We can create a `sync.WaitGroup` object in the main function and call the `Add()` method to increase the count before each goroutine starts, and then call the `Done()` method to decrease the count at the end of each goroutine. Finally, we can call the `Wait()` method to block the main function until all goroutines are completed.

The following is a sample code that demonstrates the main function waiting for other goroutines to complete:

package main
import (
"fmt"
"sync"
)
func worker(id int, wg *sync.WaitGroup) {
defer wg.Done()
fmt.Printf("Worker %d starting\n", id)
// 模拟耗时操作
for i := 0; i < 1000000000; i++ {
}
fmt.Printf("Worker %d done\n", id)
}
func main() {
var wg sync.WaitGroup
for i := 1; i <= 5; i++ {
wg.Add(1)
go worker(i, &wg)
}
wg.Wait()
fmt.Println("All workers done")
}

In the above code, we create 5 goroutines and use `sync.WaitGroup` to wait for these goroutines to complete. Each goroutine simulates a time-consuming operation and then calls the `Done()` method to decrement the count at the end. The main function calls the `Wait()` method after starting all goroutines to block until all goroutines are completed.

Summary

The main function of Go language usually waits for other goroutines to complete to ensure the correct execution of the program. However, whether the main function waits for other goroutines to complete depends on the specific code implementation. We can use `sync.WaitGroup` to implement the function of the main function waiting for other goroutines to complete.

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