clientv3/concurrency: Added Mutex.TryLock()

TryLock locks the mutex if not already locked by another session.
If lock is held by another session, return immediately after attempting necessary cleanup

Added integration test

Fixes #10493

clientv3/concurrency/example_mutex_test.go

@@ -23,6 +23,57 @@ import (
 	"go.etcd.io/etcd/clientv3/concurrency"
 )
 
+func ExampleMutex_TryLock() {
+	cli, err := clientv3.New(clientv3.Config{Endpoints: endpoints})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer cli.Close()
+
+	// create two separate sessions for lock competition
+	s1, err := concurrency.NewSession(cli)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer s1.Close()
+	m1 := concurrency.NewMutex(s1, "/my-lock/")
+
+	s2, err := concurrency.NewSession(cli)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer s2.Close()
+	m2 := concurrency.NewMutex(s2, "/my-lock/")
+
+	// acquire lock for s1
+	if err = m1.Lock(context.TODO()); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("acquired lock for s1")
+
+	if err = m2.TryLock(context.TODO()); err == nil {
+		log.Fatal("should not acquire lock")
+	}
+	if err == concurrency.ErrLocked {
+		fmt.Println("cannot acquire lock for s2, as already locked in another session")
+	}
+
+	if err = m1.Unlock(context.TODO()); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("released lock for s1")
+	if err = m2.TryLock(context.TODO()); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("acquired lock for s2")
+
+	// Output:
+	// acquired lock for s1
+	// cannot acquire lock for s2, as already locked in another session
+	// released lock for s1
+	// acquired lock for s2
+}
+
 func ExampleMutex_Lock() {
 	cli, err := clientv3.New(clientv3.Config{Endpoints: endpoints})
 	if err != nil {