CODEWITHSUNDEEP
go
K. Dackow
K. Dackow

Reputation: 456

Goroutine Termination on Calling Function Return

If I spawn a goroutine in a function and that function returns, will the goroutine terminate, or will it continue to execute?

Upvotes: 3

Views: 1686

Answers (2)

TBirkulosis
TBirkulosis

Reputation: 590

I made this example, and it shows that even though the inner function that spawned the goroutine exited, it's still running until the main exits:

package main

import (
    "bufio"
    "fmt"
    "os"
    "time"
)

func main() {
    fmt.Println("Test start")

    innerFunc()

    reader := bufio.NewReader(os.Stdin)
    fmt.Print("Press Enter to exit test: ")
    _, _ = reader.ReadString('\n')
    fmt.Println("Exiting")
}

func innerFunc() {
    fmt.Println("innerFunc()")
    go func() {
        fmt.Println("Starting goroutine")
        defer func() { fmt.Println("Exiting goroutine (doesn't get called)") }()

        for {
            fmt.Println("goroutine running")
            time.Sleep(1 * time.Second)
        }
    }()
    fmt.Println("Exiting innerFunc()")
}

Here's the output:

$ go run main.go 
Test start
innerFunc()
Exiting innerFunc()
Press Enter to exit test: Starting goroutine
goroutine running
goroutine running
goroutine running
goroutine running
goroutine running
goroutine running
goroutine running

Exiting

Upvotes: 3

iammehrabalam
iammehrabalam

Reputation: 1325

You must have to wait for all goroutine(s) to be finished in your program main thread (or say in the main method).

Let take an example

package main

import (
    "fmt"
    "time"
)

func foo() {
    go func() {
        fmt.Println("sleeping for 5 sec")
        time.Sleep(5 * time.Second)
        fmt.Println("Done")
    }()
}

func main() {
    foo()
}

When you run above code this will exit immediately (means the main thread will not wait for goroutine to finish first).

To achieve this in go I am using https://golang.org/pkg/sync/#WaitGroup

package main

import (
    "fmt"
    "sync"
    "time"
)

// see https://golang.org/pkg/sync/#WaitGroup
var wg sync.WaitGroup

func foo() {
    go func() {
        wg.Add(1)
        defer wg.Done()

        fmt.Println("sleeping for 5 sec")
        time.Sleep(5 * time.Second)
        fmt.Println("Done")
    }()
}

func main() {
    foo()
    fmt.Println("Waiting for goroutine to finish")
    wg.Wait()
    fmt.Println("All goroutine to finished")
}

Upvotes: 0

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