Add sighup, sigusr2 into trapping code, to trap signals for reloading configuration.

Need to still figure out a way of graceful restarts - gave facebookgo/httpdown a shot,
but it is not suitable.

commands.go

@@ -1,7 +1,10 @@
 package main
 
 import (
+	"os"
+	"os/signal"
 	"os/user"
+	"syscall"
 
 	"github.com/minio/cli"
 	"github.com/minio/minio/pkg/controller"
@@ -67,13 +70,33 @@ func getServerConfig(c *cli.Context) api.Config {
 	}
 }
 
+func trapServer(doneCh chan struct{}) {
+	// Go signal notification works by sending `os.Signal`
+	// values on a channel.
+	sigs := make(chan os.Signal, 1)
+
+	// `signal.Notify` registers the given channel to
+	// receive notifications of the specified signals.
+	signal.Notify(sigs, syscall.SIGHUP, syscall.SIGUSR2)
+
+	// This executes a blocking receive for signals.
+	// When it gets one it'll then notify the program
+	// that it can finish.
+	<-sigs
+	doneCh <- struct{}{}
+}
+
 func runServer(c *cli.Context) {
 	_, err := user.Current()
 	if err != nil {
 		Fatalf("Unable to determine current user. Reason: %s\n", err)
 	}
+	doneCh := make(chan struct{})
+	go trapServer(doneCh)
+
 	apiServerConfig := getServerConfig(c)
-	if err := server.StartServices(apiServerConfig); err != nil {
+	err = server.StartServices(apiServerConfig, doneCh)
+	if err != nil {
 		Fatalln(err)
 	}
 }