The main goroutine

Learn that the main function itself is a goroutine.

The main goroutine

The main function itself is a goroutine: the main goroutine. When the program starts the Go runtime launches main; when main ends all other goroutines die at once.

So if you start a goroutine and immediately exit main you never see its output. You must wait for it first: with time.Sleep, a channel or sync.WaitGroup.

time.Sleep is simple but unreliable; production code prefers channels or WaitGroup. The duration may not be enough.

Waiting methods

Three common ways to wait for goroutines:

time.Sleep: simple but fragile
sync.WaitGroup: counts, releases when zero
channel: goroutine sends a done signal

WaitGroup is the most common production choice. wg.Add(1) increments, the goroutine calls wg.Done() to decrement, the main program blocks on wg.Wait().

Exercise Print from the main goroutine

Inside main, add a fmt.Println line and print main goroutine with fmt.Println.

Show example solution

package main

import "fmt"

func main() {
    fmt.Println("ana goroutine")
}

Test yourself

What happens to goroutines when main exits?
- They are waited for
- They die immediately
- Moved to a channel
- Continue in the background
Show answer

They die immediately — they die immediately. Go goroutines cannot outlive the main program.

WaitGroup waiting

var wg sync.WaitGroup
wg.Add(1)
go func() {
    defer wg.Done()
    work()
}()
____

Show answer

var wg sync.WaitGroup
wg.Add(1)
go func() {
    defer wg.Done()
    work()
}()
wg.Wait()

Match waiting methods

time.Sleep

Fragile
WaitGroup

Production
channel

Signal
main

Main goroutine

Next lesson: Number of goroutines

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies