terminal: add way to cancel goroutines command with ctrl-C (#2278)

The goroutines command can take a long time to complete if there are
many goroutines, add the possibility to terminate it early by pressing
ctrl-C.

pkg/terminal/command.go

@@ -723,7 +723,12 @@ func goroutines(t *Term, ctx callContext, argstr string) error {
 		gslen = 0
 		gs    []*api.Goroutine
 	)
+	t.longCommandStart()
 	for start >= 0 {
+		if t.longCommandCanceled() {
+			fmt.Printf("interrupted\n")
+			return nil
+		}
 		gs, start, err = t.client.ListGoroutines(start, goroutineBatchSize)
 		if err != nil {
 			return err

pkg/terminal/terminal.go

@@ -66,6 +66,9 @@ type Term struct {
 	// should be resumed before quitting.
 	quitContinue bool
 
+	longCommandMu         sync.Mutex
+	longCommandCancelFlag bool
+
 	quittingMutex sync.Mutex
 	quitting      bool
 }
@@ -123,6 +126,7 @@ func (t *Term) Close() {
 
 func (t *Term) sigintGuard(ch <-chan os.Signal, multiClient bool) {
 	for range ch {
+		t.longCommandCancel()
 		t.starlarkEnv.Cancel()
 		state, err := t.client.GetStateNonBlocking()
 		if err == nil && state.Recording {
@@ -481,6 +485,24 @@ func (t *Term) onStop() {
 	t.printDisplays()
 }
 
+func (t *Term) longCommandCancel() {
+	t.longCommandMu.Lock()
+	defer t.longCommandMu.Unlock()
+	t.longCommandCancelFlag = true
+}
+
+func (t *Term) longCommandStart() {
+	t.longCommandMu.Lock()
+	defer t.longCommandMu.Unlock()
+	t.longCommandCancelFlag = false
+}
+
+func (t *Term) longCommandCanceled() bool {
+	t.longCommandMu.Lock()
+	defer t.longCommandMu.Unlock()
+	return t.longCommandCancelFlag
+}
+
 // isErrProcessExited returns true if `err` is an RPC error equivalent of proc.ErrProcessExited
 func isErrProcessExited(err error) bool {
 	rpcError, ok := err.(rpc.ServerError)