Goroutines in Go let functions run concurrently, using less memory than traditional threads. Every Go program starts with a main Goroutine, and if it exits, all others stop.

Example

package main

import "fmt"

func display(str string) {
    for i := 0; i < 3; i++ {
        fmt.Println(str)
    }
}

func main() {
    go display("Hello, Goroutine!")  // Runs concurrently
    display("Hello, Main!")
}

Syntax

func functionName(){
    // statements
}

// Using `go` to run as a Goroutine
go functionName()

Creating a Goroutine

To create a Goroutine, prefix the function or method call with the go keyword.

Syntax

func functionName(){
    // statements
}
// Using `go` to run as a Goroutine
go functionName()

Example:

package main
import "fmt"

func display(s string) {
    for i := 0; i < 3; i++ {
        fmt.Println(s)
    }
}

func main() {
    go display("Hello, Goroutine!")  // Runs concurrently
    display("Hello, Main!")
}

Hello, Main!
Hello, Main!
Hello, Main!

In this example, only the results from the display function in the main Goroutine appear, as the program does not wait for the new Goroutine to complete. To synchronize, we can use time.Sleep() to allow time for both Goroutines to execute.

Running Goroutines with Delay

Adding time.Sleep() allows both the main and new Goroutine to execute fully.

Example:

package main
import (
    "fmt"
    "time"
)
func display(s string) {
    for i := 0; i < 3; i++ {
        time.Sleep(500 * time.Millisecond)
        fmt.Println(s)
    }
}

func main() {
    go display("Goroutine Active")
    display("Main Function")
}

Main Function
Goroutine Active
Goroutine Active
Main Function
Goroutine Active
Main Function

Anonymous Goroutines

Anonymous functions can also be run as Goroutines by using the go keyword.

Syntax

go func(parameters) {
    // function logic
}(arguments)

Example:

package main
import (
    "fmt"
    "time"
)
func main() {
    go func(s string) {
        for i := 0; i < 3; i++ {
            fmt.Println(s)
            time.Sleep(500 * time.Millisecond)
        }
    }("Hello from Anonymous Goroutine!")

    time.Sleep(2 * time.Second) // Allow Goroutine to finish
    fmt.Println("Main function complete.")
}

Hello from Anonymous Goroutine!
Hello from Anonymous Goroutine!
Hello from Anonymous Goroutine!
Main function complete.