How to do it...

These steps cover writing and running your application:

1. From your terminal/console application, create a new directory called chapter2/signals, and navigate to that directory.
2. Copy tests from https://github.com/agtorre/go-cookbook/tree/master/chapter2/signals, or use this as an exercise to write some of your own code!
3. Create a file called signals.go with the following contents:

        package main

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

        // CatchSig sets up a listener for
        // SIGINT interrupts
        func CatchSig(ch chan os.Signal, done chan bool) {
            // block on waiting for a signal
            sig := <-ch
            // print it when it's received
            fmt.Println("nsig received:", sig)

            // we can set up handlers for all types of
            // sigs here
            switch sig {
            case syscall.SIGINT:
                fmt.Println("handling a SIGINT now!")
            case syscall.SIGTERM:
                fmt.Println("handling a SIGTERM in an entirely 
                different way!")
            default:
                fmt.Println("unexpected signal received")
            }

            // terminate
            done <- true
        }

        func main() {
            // initialize our channels
            signals := make(chan os.Signal)
            done := make(chan bool)

            // hook them up to the signals lib
            signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)

            // if a signal is caught by this go routine
            // it will write to done
            go CatchSig(signals, done)

            fmt.Println("Press ctrl-c to terminate...")
            // the program blogs until someone writes to done
            <-done
            fmt.Println("Done!")

        }

1. Run these commands:

      go build
      ./signals

1. Try running and pressing Ctrl + C, and you should see this:

      $./signals
      Press ctrl-c to terminate...
      ^C
      sig received: interrupt
      handling a SIGINT now!
      Done!

1. Try running it again and from a separate terminal, determine the PID, and kill the application:

      $./signals
      Press ctrl-c to terminate...

      # in a separate terminal
      $ ps -ef | grep signals
       501 30777 26360 0 5:00PM ttys000 0:00.00 ./signals

      $ kill -SIGTERM 30777

      # in the original terminal

      sig received: terminated
      handling a SIGTERM in an entirely different way!
      Done!

1. If you copied or wrote your own tests, go up one directory and run go test. Ensure all tests pass.