How Can 'defer' Ensure Clean Program Exit on SIGINT Signals in Go?

Signal Handling and Cleanup Using "Defer"

In programming, it is often desirable to perform cleanup or error-handling actions when interrupting a running process, such as when a user presses Ctrl C (SIGINT) to terminate the program. The "defer" keyword provides a convenient way to ensure that such actions are executed before the program exits.

Capturing the SIGINT Signal

To capture the SIGINT signal, you can use the os/signal package, which provides functions for handling incoming signals.

package main

import (
    "fmt"
    "os"
    "os/signal"
)

// main function
func main() {
    gracefulExit()
}

// Listen for and handle Ctrl+C (SIGINT) signal
func gracefulExit() {
    // Create a channel to receive signals on
    sigs := make(chan os.Signal, 1)
    
    // Register SIGINT (Ctrl+C) signal handler
    signal.Notify(sigs, os.Interrupt)

    // Start a goroutine to listen for signals
    go func() {
        sig := <-sigs
        fmt.Printf("Received %v signal. Cleaning up and exiting...\n", sig)
        
        // Trigger cleanup actions using "defer"
        defer cleanup()
        defer saveResults()
        
        os.Exit(0)
    }()
    
    // Start running the program's main logic
    runProgram()
}

Executing Defer Actions

Within the signal handling goroutine, before terminating the program, you can use the defer keyword to define cleanup actions that will be executed in reverse order of their declaration. In the example above, the cleanup() and saveResults() functions will be called before the program exits.

Customizing Cleanup Behavior

The actual cleanup actions that need to be performed when the SIGINT signal is received will vary depending on the program's specific needs. This flexibility makes signal handling and cleanup using "defer" a versatile and effective technique for managing unexpected interruptions in your code.

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