Simulating a Do-While Loop in Golang

Key Takeaways

Go does not have a built-in do...while loop, but it can be mimicked using a for loop.
A for loop with an initial true condition ensures execution at least once.
An infinite for loop with break can also simulate do...while behavior.

In Go, there isn't a built-in do...while loop as found in some other programming languages. However, you can achieve similar functionality using a for loop. A common approach is to use a for loop with a condition that ensures the loop executes at least once. Here's how you can implement it:

package main

import "fmt"

func main() {
    var input int
    for ok := true; ok; ok = (input != 2) {
        fmt.Println("Press 1 to run")
        fmt.Println("Press 2 to exit")
        _, err := fmt.Scanln(&input)
        if err != nil {
            fmt.Println("Invalid input")
            break
        }

        switch input {
        case 1:
            fmt.Println("Running...")
        case 2:
            fmt.Println("Exiting...")
            // The loop will exit naturally on the next iteration check
        default:
            fmt.Println("Invalid selection")
        }
    }
}

In this example:

We declare a variable input to store user input.
The for loop starts with ok set to true, ensuring the loop runs at least once.
After each iteration, ok is updated based on the condition (input != 2). If the user enters 2, ok becomes false, and the loop terminates.
Inside the loop, we prompt the user and read their input using fmt.Scanln.
A switch statement handles different cases based on the user's input.

This pattern effectively mimics a do...while loop, ensuring the code inside the loop executes at least once before the condition is evaluated.

Alternatively, you can use an infinite for loop with a break statement to control the loop's termination:

package main

import "fmt"

func main() {
    var input int
    for {
        fmt.Println("Press 1 to run")
        fmt.Println("Press 2 to exit")
        _, err := fmt.Scanln(&input)
        if err != nil {
            fmt.Println("Invalid input")
            continue
        }

        switch input {
        case 1:
            fmt.Println("Running...")
        case 2:
            fmt.Println("Exiting...")
            break // Exit the loop
        default:
            fmt.Println("Invalid selection")
        }
    }
}