panic: interface conversion: interface {} is nil, not chan *sarama.ProducerError

使用golang kafka sarama 包时，遇到如下问题：
高并发情况下使用同步sync producer，偶尔遇到crash:

panic: interface conversion: interface {} is nil, not chan *sarama.ProducerError

goroutine 413 [running]:
github.com/Shopify/sarama.(*syncProducer).handleSuccesses(0xc420384840)
/home/lanyang/github.com/Shopify/sarama/sync_producer.go:147 +0x139
github.com/Shopify/sarama.handleSuccesses)-fm()
/home/lanyang/src/github.com/Shopify/sarama/sync_producer.go:76 +0x2f
github.com/Shopify/sarama.withRecover(0xc4201d0750)
/home/lanyang/src/github.com/Shopify/sarama/utils.go:43 +0x45
created by github.com/Shopify/sarama.newSyncProducerFromAsyncProducer
/home/lanyang/src/github.com/Shopify/sarama/sync_producer.go:76 +0x112

问题不容易复现，github上已经留言：
https://github.com/Shopify/sarama/issues/785

download
https://github.com/Shopify/sarama
https://shopify.github.io/sarama/

doc
https://godoc.org/github.com/Shopify/sarama

依赖

github.com/davecgh/go-spew

github.com/eapache/go-resiliency
github.com/eapache/go-xerial-snappy
github.com/eapache/queue

github.com/pierrec/lz4
github.com/pierrec/xxHash

github.com/rcrowley/go-metrics

github.com/golang/snappy

如果kafka down掉，又恢复，client 可自动连接上。
异步方式，网络断开后，仍然会从queue，放入producer的channel中，重连后，这些内容丢失。

例子参考

sync
http://legendtkl.com/2016/06/30/kafka-in-action/
https://studygolang.com/articles/7102

async
https://studygolang.com/articles/11199