Goroutine and function

Learn to call a function as a goroutine.

Goroutines and functions

You can call any func as a goroutine. go greet("Alex") launches greet in the background. The function signature stays the same; only the call form changes.

Arguments are copied at the call site and passed to the goroutine. So go f(i) in a loop is safe: each goroutine gets its own i.

But if the function returns a value you cannot fetch it from the goroutine. You must send the result to a channel or write to shared state.

Goroutines in a loop

Starting many goroutines in a loop is common: for i := 0; i < 3; i++ { go f(i) }. Each iteration starts a new goroutine with its own copy of i.

Before Go 1.22 the loop variable was shared so all goroutines saw the same (last) value. Go 1.22+ fixed this: each iteration gets a fresh variable.

You still need synchronization: if main exits before goroutines finish the output is lost. Use sync.WaitGroup or a channel to wait.

Exercise Call a function as a goroutine

Inside main, add a go greet() call and print function called with fmt.Println.

Show example solution

package main

import "fmt"

func greet() {
    fmt.Println("fonksiyon çağrıldı")
}

func main() {
    go greet()
    fmt.Println("fonksiyon çağrıldı")
}

Test yourself

How is i passed in go f(i)?
- Copied by value
- Via a channel
- By reference
- As a pointer
Show answer

Copied by value — copied by value. Reference or pointer must be stated explicitly.

Goroutine call in a loop

for i := 0; i < 3; i++ {
    ____ f(i)
}

Show answer

for i := 0; i < 3; i++ {
    go f(i)
}

Match function-goroutine pairs

go f(i)

Goroutine in a loop
parameter

Copied
return

Cannot fetch directly
WaitGroup

Waiting

Next lesson: The main goroutine

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