超时后如何取消fmt.Scanf？

I have a very simple command line utility and at the end of it I'm waiting for a user to hit the enter key to end the program:

fmt.Scanf("
") // wait for hitting the enter key to end the program

Now I want to change it and if the enter key hasn't been hit for some time, I want to cancel Scanf and do something else. Is it possible to cancel waiting for user's input?

You can simply create a channel and launch a goroutine which does the fmt.Scanf(" ") and then writes something to the channel. Then select between that channel and time.After(3 * time.Second).

Here's a clean solution:

package main

import (
    "fmt"
    "time"
)

func main() {
    // Rest of the program...

    ch := make(chan int)

    go func() {
        fmt.Scanf("
")
        ch <- 1
    }()

    select {
    case <-ch:
        fmt.Println("Exiting.")
    case <-time.After(3 * time.Second):
        fmt.Println("Timed out, exiting.")
    }
}

You just need to put it in an infinate loop

package main

import (
    "fmt"
    "time"
    "context"
)

// 3 seconds for example
var deadline = time.Second * 3

func main() {
    c := make(chan string, 1)
    go scan(c)

    ctx, _ := context.WithTimeout(context.Background(), deadline)

    select {
    case <-ctx.Done():
        // didnt type for deadline seconds
    case <-c:
        // did it in time
    }
}

func scan(in chan string) {
    var input string
    _, err := fmt.Scanln(&input)
    if err != nil {
        panic(err)
    }

    in <- input
}