當(dāng)我運行下面的程序時，出現(xiàn)錯誤davecheney      tweets about golangbeertocode      does not tweet about golangironzeb         tweets about golangbeertocode      tweets about golangvampirewalk666  tweets about golangfatal error: all goroutines are asleep - deadlock!goroutine 1 [semacquire]:sync.runtime_Semacquire(0xc000010260?)        /usr/local/go/src/runtime/sema.go:56 +0x25sync.(*WaitGroup).Wait(0x100c000058058?)        /usr/local/go/src/sync/waitgroup.go:136 +0x52main.main()        /home/joe/go/src/github.com/go-concurrency-exercises/1-producer-consumer/main.go:53 +0x14f死鎖從何而來，如何改進程序以避免死鎖？package mainimport (    "fmt"    "sync"    "time")func producer(stream Stream, tweetChan chan *Tweet) {    for {        tweet, err := stream.Next()        if err == ErrEOF {            close(tweetChan)            return        }        tweetChan <- tweet        //tweets = append(tweets, tweet)    }}func consumer(tweetChan chan *Tweet) {    for t := range tweetChan {        if t.IsTalkingAboutGo() {            fmt.Println(t.Username, "\ttweets about golang")        } else {            fmt.Println(t.Username, "\tdoes not tweet about golang")        }    }}func main() {    start := time.Now()    stream := GetMockStream()    var wg sync.WaitGroup    tweetChan := make(chan *Tweet)    // Producer    //tweets := producer(stream)    wg.Add(2)    go producer(stream, tweetChan)    // Consumer    //consumer(tweets)    go consumer(tweetChan)    wg.Wait()    fmt.Printf("Process took %s\n", time.Since(start))}如果需要看mockstream.go，參考 https://github.com/loong/go-concurrency-exercises/tree/master/1-producer-consumer我的程序是原程序修改main.go的并發(fā)版本