fix:callback function execution start context being canceled (#1175)

Co-authored-by: 万玉勤 <[email protected]>

Author: wanyuqin

producer/producer.go

@@ -403,7 +403,7 @@ func (p *defaultProducer) sendAsync(ctx context.Context, msg *primitive.Message,
 
 	ctx, cancel := context.WithTimeout(ctx, p.options.SendMsgTimeout)
 	err := p.client.InvokeAsync(ctx, addr, p.buildSendRequest(mq, msg), func(command *remote.RemotingCommand, err error) {
-		cancel()
+		defer cancel()
 		if err != nil {
 			h(ctx, nil, err)
 			return