fix Azure#149 add mutex lock/unlock

sender.go

@@ -24,13 +24,14 @@ package servicebus
 
 import (
 	"context"
-	common "github.com/Azure/azure-amqp-common-go/v3"
 	"sync"
 	"time"
 
+	common "github.com/Azure/azure-amqp-common-go/v3"
+
 	"github.com/Azure/azure-amqp-common-go/v3/uuid"
-	"github.com/devigned/tab"
 	"github.com/Azure/go-amqp"
+	"github.com/devigned/tab"
 )
 
 type (
@@ -147,6 +148,9 @@ func (s *Sender) Send(ctx context.Context, msg *Message, opts ...SendOption) err
 	ctx, span := s.startProducerSpanFromContext(ctx, "sb.Sender.Send")
 	defer span.End()
 
+	s.clientMu.Lock()
+	defer s.clientMu.Unlock()
+
 	if msg.SessionID == nil {
 		msg.SessionID = &s.session.SessionID
 		next := s.session.getNext()