What Happens When the main Goroutine Exits

When the main goroutine exits, the entire program terminates immediately, killing all other running goroutines without waiting for them to finish. This behavior is inherent to the Go runtime and cannot be changed; if you need to ensure other goroutines complete their work, the main goroutine must wait for them using synchronization primitives like sync.WaitGroup.

package main

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

func main() {
	var wg sync.WaitGroup
	wg.Add(1)

	go func() {
		defer wg.Done()
		time.Sleep(2 * time.Second)
		fmt.Println("Worker finished")
	}()

	fmt.Println("Main waiting...")
	wg.Wait() // Blocks until the worker goroutine calls Done()
	fmt.Println("Program exiting")
}

The main goroutine is the boss of the program; when it leaves the room, the lights go out and everyone else is forced to stop immediately. To keep workers running until they are done, the boss must explicitly wait for them before leaving. Think of it like a manager who must stay until their team finishes a project before closing the office.