How to Handle Invalid User Input in Go: Flushing Stdin and Alternatives

Understanding Input Consumption in Go: Flushing and Alternatives

When interacting with users through the terminal, handling invalid input can be challenging. In Go, using fmt.Scanf() to read input may encounter issues when users enter non-integer values. This is because fmt.Scanf() doesn't consume the entire line, leaving residual characters that may interfere with subsequent input.

To address this issue, one option is to explicitly flush the input buffer after an invalid entry. However, Go does not provide a direct method for flushing Stdin.

Alternative Approaches:

1. Using fmt.Scanln(): fmt.Scanln() reads a line of input, including spaces and newlines. It consumes the entire line, eliminating the need for explicit flushing.

<code class="go">fmt.Println("Please enter an integer:")
var userI int
_, err := fmt.Scanln(&userI)
if err != nil {
    fmt.Println("Sorry, invalid input. Please try again:")
}</code>

2. Custom Input Handling: Create a custom function to read and validate user input, consuming and discarding invalid entries until valid input is obtained.

<code class="go">func GetUserInputInt() int {
    var userI int
    for {
        fmt.Println("Please enter an integer:")
        _, err := fmt.Scanf("%d", &userI)
        if err == nil {
            return userI
        }
        fmt.Println("Sorry, invalid input. Please try again:")
        fmt.Scanln() // Discard invalid input
    }
}</code>

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