tour:explanation for "For is Go's "while"" is not enough!

[Mehdi-orang]

I don't know below code how computing the out!!
https://tour.golang.org/flowcontrol/3

package main

import "fmt"

func main() {
sum := 1
for sum < 9 {
sum += sum
}
fmt.Println(sum)
}

[ghost]

Try something like this?

 package main
 
 import "fmt"
 
 func main() {
 	sum := 1
 	for sum < 9 {
+		fmt.Println(sum)
 		sum += sum
 	}
 	fmt.Println(sum)
 }