Menu
In Go, all goroutines can read and write the same global variables, or objects shared across threads, so data races are possible.
Another way to synchronize access to a shared resource is by using a mutex . A mutex is named after the concept of mutual exclusion. A mutex is used to create a critical section around code that ensures only one goroutine at a time can execute that code section.
In Go, concurrency works through the use of in-built functions known as Goroutines. Goroutines are functions, unique to Go, that run at the same time alongside other code or programs. They're not OS threads, though, they may be considered lightweight threads. Goroutines are deeply integrated with Go's runtime.
The go statement runs a function in a separate thread of execution. You can start a new thread of execution, a goroutine, with the go statement. It runs a function in a different, newly created, goroutine. All goroutines in a single program share the same address space.
I'm learning Go and trying to understand its concurrency features.
I have the following program.
package main
import (
"fmt"
"sync"
)
func main() {
var wg sync.WaitGroup
for i := 0; i < 5; i++ {
wg.Add(1)
x := i
go func() {
defer wg.Done()
fmt.Println(x)
}()
}
wg.Wait()
fmt.Println("Done")
}
When executed I got:
4
0
1
3
2
It's just what I want. However, if I make slight modification to it:
package main
import (
"fmt"
"sync"
)
func main() {
var wg sync.WaitGroup
for i := 0; i < 5; i++ {
wg.Add(1)
go func() {
defer wg.Done()
fmt.Println(i)
}()
}
wg.Wait()
fmt.Println("Done")
}
What I got will be:
5
5
5
5
5
I don't quite understand the difference. Can anyone help to explain what happened here and how Go runtime execute this code?
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With