btcwallet: handle signal SIGTERM

When an OS reboots or shuts down, it sends all processes SIGTERM before
sending SIGKILL.  This allows btcwallet to do a proper shutdown which
most importantly closes the databases.

signal.go

@@ -22,6 +22,10 @@ var interruptHandlersDone = make(chan struct{})
 
 var simulateInterruptChannel = make(chan struct{}, 1)
 
+// signals defines the signals that are handled to do a clean shutdown.
+// Conditional compilation is used to also include SIGTERM on Unix.
+var signals = []os.Signal{os.Interrupt}
+
 // simulateInterrupt requests invoking the clean termination process by an
 // internal component instead of a SIGINT.
 func simulateInterrupt() {
@@ -49,8 +53,8 @@ func mainInterruptHandler() {
 
 	for {
 		select {
-		case <-interruptChannel:
+		case sig := <-interruptChannel:
-			log.Info("Received SIGINT (Ctrl+C).  Shutting down...")
+			log.Infof("Received signal (%s).  Shutting down...", sig)
 			invokeCallbacks()
 			return
 		case <-simulateInterruptChannel:
@@ -71,7 +75,7 @@ func addInterruptHandler(handler func()) {
 	// all other callbacks and exits if not already done.
 	if interruptChannel == nil {
 		interruptChannel = make(chan os.Signal, 1)
-		signal.Notify(interruptChannel, os.Interrupt)
+		signal.Notify(interruptChannel, signals...)
 		go mainInterruptHandler()
 	}
 

signalsigterm.go

@@ -0,0 +1,16 @@
+// Copyright (c) 2016 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package main
+
+import (
+	"os"
+	"syscall"
+)
+
+func init() {
+	signals = []os.Signal{os.Interrupt, syscall.SIGTERM}
+}