time.After() Function in Golang With Examples

In Go language, time packages supplies functionality for determining as well as viewing time. The After() function in Go language is used to wait for the duration of time to pass and after that it delivers the actual time on the returned channel. Moreover, this function is defined under the time package. Here, you need to import “time” package in order to use these functions.

Syntax:

func After(d Duration) <-chan Time

Here, d is the duration of time before time out, and chan is the channel where current time is sent.

Return Value: It first waits for the stated time and then displays timeout.

Example 1:

// Golang program to illustrate the usage of
// After() function in Golang

// Including main package
package main

// Importing fmt and time
import (
    "fmt"
    "time"
)

// Creating a channel
// Using var keyword
var ch chan int

// Main function
func main() {

    // For loop
    for i := 1; i < 6; i++ {

        // Prints these util loop stops
        fmt.Println("****Welcome to GeeksforGeeks***")
        fmt.Println("A CS-Portal!")
    }

    // Select statement
    select {

    // Using case statement to receive
    // or send operation on channel and
    // calling After() method with its
    // parameter
    case <-time.After(3 * time.Second):

        // Printed when timed out
        fmt.Println("Time Out!")
    }
}

Output:

****Welcome to GeeksforGeeks***
A CS-Portal!
****Welcome to GeeksforGeeks***
A CS-Portal!
****Welcome to GeeksforGeeks***
A CS-Portal!
****Welcome to GeeksforGeeks***
A CS-Portal!
****Welcome to GeeksforGeeks***
A CS-Portal!
Time Out!    // Displayed after 3 seconds as mentioned in the above code

In the above example, we have used the “case” statement under the select statement in order to send operation on the channel. Moreover, here time out will be displayed after 3 seconds of the execution of for loop.

Example 2:

// Golang program to illustrate the usage of
// After() function in Golang

// Including main package
package main

// Importing fmt and time
import (
    "fmt"
    "time"
)

// Main function
func main() {

    // Creating a channel
    // Using make keyword
    channel := make(chan string, 2)

    // Select statement
    select {

    // Using case statement to receive
    // or send operation on channel
    case output := <-channel:
        fmt.Println(output)

    // Calling After() method with its
    // parameter
    case <-time.After(5 * time.Second):

        // Printed after 5 seconds
        fmt.Println("Its timeout..")
    }
}

Output:

Its timeout..

Here, we have used the “make” keyword in order to create a channel then like the above example here also case statement is used under a select statement but here it’s used twice. The first one is used to return output and the second one is used to call After() method on the channel. After this, the timeout is displayed in the stated time.