file read - write 

package main

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

func main() {
 // file name
 fileName := "myFile.txt"

 if _, err := os.Stat(fileName); os.IsNotExist(err) {
  
  // create a file
  _, err := os.Create(fileName)
  checkError(err)
  
  fmt.Println(fileName + " is created.")
 } else {
  // file exists
  fmt.Println(fileName + " exists.")
 }

 // For read access.
 fileData, err := os.OpenFile(fileName, os.O_WRONLY|os.O_APPEND, 0666)
 checkError(err)

 fileStat, err := os.Stat(fileName)
 checkError(err)

 if fileStat.Size() == 0 {
  fmt.Println("It is fresh!")
 }

 reader := bufio.NewReader(os.Stdin)
 fmt.Print("\nText: ")

 content, _ := reader.ReadString('\n')

 ln, err := io.WriteString(fileData, content)
 checkError(err)
 fmt.Printf("%v character is included.", ln-1)

 fileData.Close()
}

func checkError(err error) {
 if err != nil {
  panic(err)
 }
}