How to run 2 goroutines in a specific order-CodePudding

I want to execute 2 goroutines sequentially, one after another.

For example, I have following goroutines called in main function:

go func1()
go func2()

And I want that func1() should first complete its execution and then only func2() should execute, every time when I run my main function.

How can I achieve this ordering in goroutines?

Thanks.

CodePudding user response：

To ensure sequential execution of functions, run the functions in a single goroutine:

go func() {
    func1()
    func2()
}()

CodePudding user response：

If you really want them as separate goroutines (why?) you need to synchronize them. You can use channels, mutexes, or other concurrency primitives. The example below accomplishes that with a signaling channel:

ch := make(chan struct{})
go func() {
  func1()
  close(ch)
}
go func() {
  <-ch
  func2()
}

Playground: https://go.dev/play/p/ZqHz-ILpA2J

EDIT: Following Paul Hankin's advice, using close(ch) instead of ch <- struct{}{} to signal completion.

CodePudding user response：

For squentially running go routine , you should always use sync package

package main

import (
    "fmt"
    "sync"
)

func main() {

    var w sync.WaitGroup

    w.Add(1)
    go fun1(&w)
    w.Wait()
    
    w.Add(1)
    go  fun2(&w)
    w.Wait()


}

func fun1(w *sync.WaitGroup) {
    i:=1000
    for i>0{
        i-=1
    }
    fmt.Println("fun1")
    defer   w.Done()
}

func fun2(w *sync.WaitGroup) {
    fmt.Println("fun2")
    defer w.Done()

}