Signal handling, force quit after two interrupts

packer.go

@@ -96,6 +96,8 @@ func main() {
 		os.Exit(1)
 	}
 
+	setupSignalHandlers(env)
+
 	exitCode, err := env.Cli(os.Args[1:])
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error executing CLI: %s\n", err.Error())

signal.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"github.com/mitchellh/packer/packer"
+	"github.com/mitchellh/packer/packer/plugin"
+	"log"
+	"os"
+	"os/signal"
+)
+
+// Prepares the signal handlers so that we handle interrupts properly.
+// The signal handler exists in a goroutine.
+func setupSignalHandlers(env packer.Environment) {
+	ch := make(chan os.Signal, 1)
+	signal.Notify(ch, os.Interrupt)
+
+	go func() {
+		<-ch
+		log.Println("First interrupt. Ignoring, will let plugins handle...")
+		<-ch
+		log.Println("Second interrupt. Exiting now.")
+
+		env.Ui().Error("Interrupt signal received twice. Forcefully exiting now.")
+
+		// Force kill all the plugins
+		plugin.CleanupClients()
+		os.Exit(1)
+	}()
+}