Added integration test

Author: cmaglie

internal/integrationtest/daemon/daemon_concurrency_test.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"sync"
 	"testing"
 	"time"
 
@@ -76,3 +77,51 @@ func TestArduinoCliDaemonCompileWithLotOfOutput(t *testing.T) {
 	testCompile()
 	testCompile()
 }
+
+func TestInitAndMonitorConcurrency(t *testing.T) {
+	// See: https://github.com/arduino/arduino-cli/issues/2719
+
+	env, cli := integrationtest.CreateEnvForDaemon(t)
+	defer env.CleanUp()
+
+	_, _, err := cli.Run("core", "install", "arduino:avr")
+	require.NoError(t, err)
+
+	grpcInst := cli.Create()
+	require.NoError(t, grpcInst.Init("", "", func(ir *commands.InitResponse) {
+		fmt.Printf("INIT> %v\n", ir.GetMessage())
+	}))
+
+	cli.InstallMockedSerialMonitor(t)
+
+	// Open the serial monitor for 5 seconds
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	mon, err := grpcInst.Monitor(ctx, &commands.Port{
+		Address:  "/dev/test",
+		Protocol: "serial",
+	})
+	require.NoError(t, err)
+	var monitorCompleted sync.WaitGroup
+	monitorCompleted.Add(1)
+	go func() {
+		for {
+			msg, err := mon.Recv()
+			if err != nil {
+				break
+			}
+			fmt.Println("MON> ", msg)
+		}
+		fmt.Println("MON CLOSED")
+		monitorCompleted.Done()
+	}()
+
+	// Check that Init completes without blocking when the monitor is open
+	start := time.Now()
+	require.NoError(t, grpcInst.Init("", "", func(ir *commands.InitResponse) {
+		fmt.Printf("INIT> %v\n", ir.GetMessage())
+	}))
+	require.LessOrEqual(t, time.Since(start), 4*time.Second)
+	cancel()
+	monitorCompleted.Wait()
+}