Now forwarding all signals to process group

By doing this, we make sure piping through zap-pretty will still send all
signals to the process group ensuring they can do signal handling themselves
removing some weird problem killing process can bring.

main.go

@@ -61,6 +61,8 @@ func main() {
 		os.Exit(0)
 	}
 
+	go NewSignaler().forwardAllSignalsToProcessGroup()
+
 	processor := &processor{
 		scanner: bufio.NewScanner(os.Stdin),
 		output:  os.Stdout,

signaler.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+type signaler struct {
+	processGroupID int
+}
+
+func NewSignaler() *signaler {
+	signaler := &signaler{}
+
+	pgid, err := syscall.Getpgid(os.Getpid())
+	if err != nil {
+		signaler.processGroupID = pgid
+	} else {
+		debug.Println("[Warning] unable to determine process group, signaling will be broken")
+	}
+
+	return signaler
+}
+
+func (s *signaler) forwardAllSignalsToProcessGroup() {
+	signalChan := make(chan os.Signal, 1)
+	signal.Notify(signalChan)
+
+	for {
+		signal := <-signalChan
+
+		syscallSignal, isSyscallSignalType := signal.(syscall.Signal)
+		if s.processGroupID != 0 && isSyscallSignalType {
+			syscall.Kill(s.processGroupID, syscallSignal)
+		}
+	}
+}