Goで文字列の置き換えをする(strings packageのReplace) ref: https://qiita.com/Sekky0905/items/f0bed43ad3ab4be13385

file0.go

package main

import (
    "fmt"
    "strings"
)

func main() {
    str := "Go Java JavaScript Typescript CofeeScript"
    // 普通に表示
    fmt.Printf("str : %s\n", str)

    // 最初の"Java"という文字列だけ置き換え
    replaced1 := strings.Replace(str, "Java", "Replaced", 1)
    fmt.Printf("replaced1 : %s\n", replaced1)

    // 全部のJavaを置き換え
    replaced2 := strings.Replace(str, "Java", "Replaced", -1)
    fmt.Printf("replaced2 : %s\n", replaced2)

    // 全部のScriptを置き換え
    // Typescriptの"script"は小文字のため、変更されない
    replaced3 := strings.Replace(str, "Script", "Replaced", -1)
    fmt.Printf("replaced3 : %s\n", replaced3)

}

file1.txt

str : Go Java JavaScript Typescript CofeeScript
replaced1 : Go Replaced JavaScript Typescript CofeeScript
replaced2 : Go Replaced ReplacedScript Typescript CofeeScript
replaced3 : Go Java JavaReplaced Typescript CofeeReplaced