Command line and server-style application often allow you to press a key combination, such as CTRL+C to gracefully exit. In Go this is a pretty easy task to accomplish, and in this entry I will show you how you can add this ability in your own applications.

First off, CTRL+C is referred to, especially in the *nix world, a signal. The proper name for the signal sent to your application when you press CTRL+C is SIGINT. This is short for an interrupt signal. The Go standard library has support for receiving and handling signals in your application.

To handle SIGINT in your application you need to perform three steps

1. Setup a channel to receive a notification when the signal occurs
2. Setup the notification to be sent to that channel
3. Have a goroutine that loops and waits until something is received on that channel

For this example let’s look at how we can listen for SIGINT and simply exit the application when that signal is received.

import (
    "os"
    "os/signal"
)

func main() {
    // Setup a channel to receive a signal
    done := make(chan os.Signal, 1)

    // Notify this channel when a SIGINT is received
    signal.Notify(done, os.Interrupt)

    // Fire off a goroutine to loop until that channel receives a signal.
    // When a signal is received simply exit the program
    go func() {
        for _ = range done {
            os.Exit(0)
        }
    }()
}

The tools to handle signals are part of the standard Go library. In lines 1 - 4 we see the imports for this lie in the os and os/signal packages. After importing the necessary libraries we then setup a channel which has room for a single item of type os.Signal. Then we call Notify() to write to the channel when a SIGINT (os.Interrupt) is received.

Finally we spawn a goroutine that starts a loop that will block execution until that channel receives something. When it does we are simply exiting the application by calling os.Exit(). Now let’s look at a version of this that uses a little package I put together that you can find on Github.

import (
    "os"

    "github.com/adampresley/sigint"
)

func main() {
    sigint.ListenForSIGINT(func() {
        os.Exit(0)
    })
}

Notice that the code is similar, but this package allows you to call a function, passing in another function that will be executed when a SIGINT is fired off to your application.

Cheers, and happy coding!