我在從兩個(gè)通道接收的 go 例程中有一個(gè) select 語句。for {    fmt.Printf("Waiting for select statement ...\n")    select {    case req := <-requestChan:        fmt.Printf("I got a request: %v\n", req)    case <-doneChan:        fmt.Printf("serveDatabase: Got closing signal. Stop serving.\n")        return    }}如果調(diào)用函數(shù)發(fā)送到第一個(gè)通道兩次，然后發(fā)送到第二個(gè)通道，一切正常：requestChan <- Db_request{ request: "Login", beehive: "yaylaswiese" }requestChan <- Db_request{ request: "Signup", beehive: "aziz nezir" }fmt.Printf("Sending true to the doneChannel\n")doneChan <- true控制臺(tái)輸出（正確）是：>     Waiting for select statement ...>     I got a request: {Login yaylaswiese}>     Waiting for select statement ...>     Sending true to the doneChannel>     I got a request: {Signup aziz nezir}>     Waiting for select statement ...>     serveDatabase: Got closing signal. Stop serving.但是，如果我評(píng)論第二個(gè)請(qǐng)求，例如requestChan <- Db_request{ request: "Login", beehive: "yaylaswiese" }// requestChan <- Db_request{ request: "Signup", beehive: "aziz nezir" }fmt.Printf("Sending true to the doneChannel\n")doneChan <- true然后輸出是>     Waiting for select statement ...>     I got a request: {Login yaylaswiese}>     Waiting for select statement ...>     Sending true to the doneChannel所以doneChan 永遠(yuǎn)不會(huì)收到。我也嘗試在發(fā)送 doneChan 后進(jìn)入無限循環(huán)，但結(jié)果相同。那可能是什么？