tt: add using channels instead of contexts to handle signals

Author: vr009

cli/running/running.go

@@ -20,7 +20,6 @@ import (
 	"github.com/tarantool/tt/cli/process_utils"
 	"github.com/tarantool/tt/cli/ttlog"
 	"github.com/tarantool/tt/cli/util"
-	"golang.org/x/net/context"
 	"gopkg.in/yaml.v2"
 )
 
@@ -516,18 +515,19 @@ func FillCtx(cliOpts *config.CliOpts, cmdCtx *cmdcontext.CmdCtx,
 
 // Start an Instance.
 func Start(cmdCtx *cmdcontext.CmdCtx, run *InstanceCtx) error {
-	// Register a context, related with a signal handler that
-	// removes a pid file if interrupt signals were sent before starting
-	// an instance and watchdog signal handlers.
-	sigCtx, stop := signal.NotifyContext(context.Background(),
+	// Register a signal handler that removes a pid file if interrupt
+	// signals were sent to the process before starting an instance
+	// and watchdog signal handlers.
+	signalChan := make(chan os.Signal, 1)
+	signal.Notify(signalChan,
 		syscall.SIGINT, syscall.SIGTERM)
 	if err := process_utils.CreatePIDFile(run.PIDFile); err != nil {
 		return err
 	}
 
 	defer func() {
 		cleanup(run)
-		stop()
+		signal.Stop(signalChan)
 	}()
 
 	logger := createLogger(run)
@@ -537,9 +537,14 @@ func Start(cmdCtx *cmdcontext.CmdCtx, run *InstanceCtx) error {
 	// The Done() state of the context means that the process received
 	// an interrupt signal and there is a need to clean up the resources.
 	select {
-	case <-sigCtx.Done():
+	case <-signalChan:
 		return nil
 	default:
+		// Ignore function unregisters the current signal handler.
+		// SIGINT and SIGTERM signals will be ignored until the call of
+		// signal.Reset(), that will be done before the start of
+		// watchdog's signal handling loop.
+		signal.Ignore(syscall.SIGINT, syscall.SIGTERM)
 		wd.Start()
 	}
 	return nil

cli/running/watchdog.go

@@ -111,9 +111,6 @@ func (wd *Watchdog) Start() {
 // startSignalHandling starts signal handling in a separate goroutine.
 func (wd *Watchdog) startSignalHandling() {
 	sigChan := make(chan os.Signal, 1)
-	// Reset unregisters all previous handlers for interrupt signals.
-	signal.Reset(syscall.SIGINT,
-		syscall.SIGTERM, syscall.SIGHUP)
 	signal.Notify(sigChan)
 
 	// Set barrier to synchronize with the main loop when the Instance stops.