Implement graceful shutdown on Mac (#619)

* hold cleanup until procKilledCh signal

* signal to procKilledChan in existing deferred func

* without this can't exit when non zero exit code

it seems like `os.Exit(state.ExitCode())` belongs here... but unclear on intent of `e.config.Build.Rerun`

This at least lets you ctrl+c out of error condition instead of killing pid via external means.

* Revert "without this can't exit when non zero exit code"

This reverts commit fec348c.

* use cleanup

* fix test case rerun

* upgrade gomod version

* remove unused `WaitGroup`

---------

Co-authored-by: Seth Brasile <seth.brasile@gmail.com>

Author: xiantang

runner/engine.go

@@ -31,6 +31,7 @@ type Engine struct {
 	binStopCh      chan bool
 	exitCh         chan bool
 
+	procKillWg    sync.WaitGroup
 	mu            sync.RWMutex
 	watchers      uint
 	fileChecksums *checksumMap
@@ -478,8 +479,7 @@ func (e *Engine) runPostCmd() error {
 }
 
 func (e *Engine) runBin() error {
-	killFunc := func(cmd *exec.Cmd, stdout io.ReadCloser, stderr io.ReadCloser, killCh chan struct{}, processExit chan struct{}, wg *sync.WaitGroup) {
-		defer wg.Done()
+	killFunc := func(cmd *exec.Cmd, stdout io.ReadCloser, stderr io.ReadCloser, killCh chan struct{}, processExit chan struct{}) {
 		select {
 		// listen to binStopCh
 		// cleanup() will close binStopCh when engine stop
@@ -518,13 +518,11 @@ func (e *Engine) runBin() error {
 
 	e.runnerLog("running...")
 	go func() {
-		wg := sync.WaitGroup{}
 
 		defer func() {
 			select {
 			case <-e.exitCh:
 				e.mainDebug("exit in runBin")
-				wg.Wait()
 			default:
 			}
 		}()
@@ -536,6 +534,7 @@ func (e *Engine) runBin() error {
 			case <-killCh:
 				return
 			default:
+				e.procKillWg.Add(1)
 				command := strings.Join(append([]string{e.config.Build.Bin}, e.runArgs...), " ")
 				cmd, stdout, stderr, _ := e.startCmd(command)
 				processExit := make(chan struct{})
@@ -544,11 +543,10 @@ func (e *Engine) runBin() error {
 					e.proxy.Reload()
 				}
 
-				wg.Add(1)
 				e.withLock(func() {
 					close(e.binStopCh)
 					e.binStopCh = make(chan bool)
-					go killFunc(cmd, stdout, stderr, killCh, processExit, &wg)
+					go killFunc(cmd, stdout, stderr, killCh, processExit)
 				})
 
 				go func() {
@@ -570,6 +568,7 @@ func (e *Engine) runBin() error {
 				default:
 					e.runnerLog("Process Exit with Code: %v", state.ExitCode())
 				}
+				e.procKillWg.Done()
 
 				if !e.config.Build.Rerun {
 					return
@@ -621,7 +620,7 @@ func (e *Engine) cleanup() {
 	}
 
 	e.mainDebug("waiting for exit...")
-
+	e.procKillWg.Wait()
 	e.running = false
 	e.mainDebug("exited")
 }