How to replicate do while in go? - for-loop

Question

I want a set of code to be executed until user explicitly wants to exit the function. For eg: when a user runs the program, he will see 2 options:
Run again
Exit
this will be achieved using switch case structure. Here if user presses 1, set of functions associated with 1 will execute and if user presses 2, the program will exit. How should i achieve this scenario in golang ? In java, i believe this could be done using do while structure but go doesn't support do while loop. Following is my code which i tried but this goes in a infinite loop:
func sample() {
var i = 1
for i > 0 {
fmt.Println("Press 1 to run")
fmt.Println("Press 2 to exit")
var input string
inpt, _ := fmt.Scanln(&input)
switch inpt {
case 1:
fmt.Println("hi")
case 2:
os.Exit(2)
default:
fmt.Println("def")
}
}
}
The program irrespective of the input, prints only "hi". Could someone please correct me what wrong i am doing here ?
Thanks.

Answer 1

A do..while can more directly be emulated in Go with a for loop using a bool loop variable seeded with true.
for ok := true; ok; ok = EXPR { }
is more or less directly equivalent to
do { } while(EXPR)
So in your case:
var input int
for ok := true; ok; ok = (input != 2) {
n, err := fmt.Scanln(&input)
if n < 1 || err != nil {
fmt.Println("invalid input")
break
}
switch input {
case 1:
fmt.Println("hi")
case 2:
// Do nothing (we want to exit the loop)
// In a real program this could be cleanup
default:
fmt.Println("def")
}
}
Edit: Playground (with a dummied-out Stdin)
Though, admittedly, in this case it's probably overall clearer to just explicitly call (labelled) break, return, or os.Exit in the loop.

Answer 2

When this question was asked this was a better answer for this specific scenario (little did I know this would be the #1 result when searching Google for "do while loop golang"). For answering this question generically please see #LinearZoetrope's answer below.
Wrap your function in a for loop:
package main
import (
"fmt"
"os"
)
func main() {
fmt.Println("Press 1 to run")
fmt.Println("Press 2 to exit")
for {
sample()
}
}
func sample() {
var input int
n, err := fmt.Scanln(&input)
if n < 1 || err != nil {
fmt.Println("invalid input")
return
}
switch input {
case 1:
fmt.Println("hi")
case 2:
os.Exit(2)
default:
fmt.Println("def")
}
}
A for loop without any declarations is equivalent to a while loop in other C-like languages. Check out the Effective Go documentation which covers the for loop.

Answer 3

The do...while in go can be this:
func main() {
var value int
for {
value++
fmt.Println(value)
if value%6 != 0 {
break
}
}
}

Answer 4

a while loop in Go can be as easy as this:
package main
import `fmt`
func main() {
for {
var number float64
fmt.Print(`insert an Integer eq or gr than 10!!!`)
fmt.Scanf(`%f`, &number)
if number >= 10 { break }
fmt.Println(`sorry the number is lower than 10....type again!!!`)
}

Answer 5

Conside to use "for-break" as "do-while".
foo.go
package main
import (
"fmt"
)
func main() {
i := 0
for {
i++
if i > 10 {
break
}
fmt.Printf("%v ", i)
}
fmt.Println()
}
shell
$ go run foo.go
1 2 3 4 5 6 7 8 9 10

Answer 6

Maybe not what you're looking for, but if you're trying to do something like this:
int i = 0;
while (i < 10) {
cout << "incrementing i now" << endl;
i++
}
cout << "done"
You'll have to do something like this in go:
var i = 0
fmt.Println(i)
for {
if i < 10 {
fmt.Println("incrementing i now")
i++
} else {
break
}
}
fmt.Println("done")

Answer 7

sum := 1
for sum < 1000 {
sum += sum
}
Explanation :
The basic for loop has three components separated by semicolons:
-the init statement: executed before the first iteration.
-the condition expression: evaluated before every iteration
-the post statement: executed at the end of every iteration
The init and post statements are optional.
So you can just put in the condition expression.
// While (CONDITION = true){
//code to execute ....}
//In go :
for CONDITION = true {
//code to execute}

Answer 8

This is one of the cleanest ways:
num := 10
for num > 0 {
// do stuff here
num--
}