go - 简单消息客户端 golang

Question

所以我开始了一个项目，该项目涉及通过 websockets 从服务器发送和接收消息的模块。但是，我想要一种简单的方式来与模块交互并向模块发送消息。

所以我让程序在 goroutine 中询问我的消息，当我按下回车键时，它会发送消息并提示我输入另一条消息。在主 goroutine 中，它会一直等到它收到一条消息，当它收到消息时，覆盖当前行并在新行中替换之前行中的内容。

然而，只有一个问题。它不知道如何将我的输入放在新行上。在我使用以下示例进行的测试中，os.Stdin.Read 似乎会停止，直到它收到换行符。

package main

import (
    "bufio"
    "fmt"
    "os"
    "time"
)

func main() {
    // Input Buffer
    var msg string

    scanner := bufio.NewScanner(os.Stdin)
    scanner.Split(bufio.ScanBytes)

    go func() {
        for {
            // Prompt the user for a message
            fmt.Print("client1: ")

            // Scan os.Stdin, splitting on bytes
            for scanner.Scan() {
                if scanner.Text() == "\n" {
                    break
                } else {
                    // If the character is not \n, add to the input buffer
                    msg += scanner.Text()
                }
            }

            // Do something with the input buffer then clear it
            fmt.Println(msg)
            msg = ""
        }
    }()

    for {
        select {
        // Receive a message from a client
        case <-time.After(5 * time.Second):
            // Write the message over the current line
            fmt.Println("\rclient2: Hello")

            // Prompt the user again for their message
            // proving the current input buffer
            fmt.Print("client1: " + msg)
        }
    }
}

示例输出:

client1: Hello!
Hello!
client2: Hello
client1: Bye!
Bye!
client2: Hello
client2: Hello // Was "client1: Good " before being overwritten
client1: Bye!
Good Bye!

非常感谢任何想法。先谢谢你。

Answer 1

这似乎是 IO 竞争条件。您的 goroutine 未与 main 同步。顺便说一句，ScanLines 会为您做同样的事情。考虑一下:

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    scanner := bufio.NewScanner(os.Stdin)
    msgQ := make(chan string)

    defer close(msgQ)

    go func() {
        for {
            // Prompt the user for a message
            fmt.Print("client1: ")
            msg, ok := <-msgQ
            if !ok {
                return
            }
            fmt.Println("\rclient1 said: " + msg)
            // Write the message over the current line
            fmt.Println("client2: Hello")
        }
    }()


    // Scan os.Stdin, splitting on bytes
    for scanner.Scan() {
        msgQ <- scanner.Text()
    }

}

编辑:根据评论，此代码显示了该想法的错误之处。当你写东西但不按 ENTER 键时，client2 会覆盖当前行。你可以保存(CTRL-U)和恢复(CTRL-Y)当前行，但我没有找到 ANSI 签名或 Signal 以编程方式调用它。

package main

import (
    "bufio"
    "fmt"
    "os"
    "time"
)

func main() {

    scanner := bufio.NewScanner(os.Stdin)
    sendQ := make(chan struct{})

    defer close(sendQ)

    //simulate local client1 console
    go func() {
        for {
            fmt.Print("client1: ")
            select {
            case _, ok := <-sendQ:
                if !ok {
                    return
                }
            case <-time.After(5 * time.Second):
                fmt.Printf("\r\033[K") // delete current line from right
                fmt.Println("client2: Hello")
            }
        }
    }()

    for scanner.Scan() {
        sendQ <- struct{}{}
    }

}