package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
   scanner := bufio.NewScanner(os.Stdin)
   scanner.Scan()
   in := scanner.Text()

   in2 := []byte(in)

   for i,j := 0,len(in2)-1;i < j;j--{
    in2[i],in2[j] = in2[j],in2[i]
    i++
   }

   fmt.Println(string(in2))

}

什么颠倒，反转统一用双指针