Goroutine Lifecycle

In this lesson, explore goroutine lifecycle through one small Go program, and connect its output to the language rules behind it.

A goroutine is created, scheduled, can block while waiting for data or a lock, and eventually returns. Returning from main ends the process; other goroutines are not automatically joined.

A clear lifetime contract identifies who starts the task, what can stop it, and who waits for it.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import (
	"fmt"
	"sync"
)

func main() {
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		fmt.Println("Worker completed")
	}()
	wg.Wait()
	fmt.Println("Main can exit")
}

Output

Worker completed
Main can exit

Wait keeps the main goroutine active until the worker calls Done. The deferred call also runs on normal return from the worker.

• Do not use arbitrary sleep durations as a completion guarantee.
• If Done is never called, Wait can remain blocked.

Create two workers and ensure both report completion before main exits.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Goroutine Lifecycle in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.