goto实现判断函数
#include <stdio.h>
void main() {
int age;
gotolabel: //注意是：
printf("You are not eligible to vote!\n");
printf("Enter you age:\n");
scanf("%d", &age);
if (age < 18) {
goto gotolabel; //跳转到gotolabel
}else {
printf("You are eligible to vote!\n");
}
}