golang strings Replace 字符串替换

函数声明为：

func Replace(s, old, new string, n int) string

官方描述为：返回将s中前n个不重叠old子串都替换为new的新字符串，如果n<0会替换所有old子串。
示例代码为，每行的结果见每行上面的注释部分：

func main() {
    // non-overlapping: "123" repeat 6 times in s
    s := "123lafaldsjglad123lkfasdf123djfal123lkdjga123lksjfla123l"
    old := "123"
    new := "888"
    
    fmt.Println("non-overlapping: ")
     // n < 0 ,用 new 替换所有匹配上的 old；n=-1:  888lafaldsjglad888lkfasdf888djfal888lkdjga888lksjfla888l
    fmt.Println("n=-1: ", strings.Replace(s, old, new, -1 ))
    
    // 不替换任何匹配的 old；n=0:  123lafaldsjglad123lkfasdf123djfal123lkdjga123lksjfla123l
    fmt.Println("n=0: ", strings.Replace(s, old, new, 0 )) 

    // 用 new 替换第一个匹配的 old；n=1:  888lafaldsjglad123lkfasdf123djfal123lkdjga123lksjfla123l
    fmt.Println("n=1: ", strings.Replace(s, old, new, 1 ))

    // 用 new 替换前 5 个匹配的 old（实际多于 5 个）；n=5:  888lafaldsjglad888lkfasdf888djfal888lkdjga888lksjfla123l
    fmt.Println("n=5: ", strings.Replace(s, old, new, 5 )) 
    
    // 用 new 替换前 7 个匹配上的 old（实际没那么多）；n=7:  888lafaldsjglad888lkfasdf888djfal888lkdjga888lksjfla888l
    fmt.Println("n=7: ", strings.Replace(s, old, new, 7 )) 

    // overlapping:
    s = "888888888888888888"
    old = "888"
    new = "666"
    fmt.Println("overlapping: ")

    // n < 0 ,用 new 替换所有匹配上的 old；n=-1:  666666666666666666
    fmt.Println("n=-1: ", strings.Replace(s, old, new, -1 )) 

    // 不替换任何匹配的 old；n=0:  888888888888888888
    fmt.Println("n=0: ", strings.Replace(s, old, new, 0 )) 
  
    // 用 new 替换第一个匹配的 old；n=1:  666888888888888888
    fmt.Println("n=1: ", strings.Replace(s, old, new, 1 )) 

     // 用 new 替换前 5 个匹配的 old（实际多于 5 个）；n=5:  666666666666666888
    fmt.Println("n=5: ", strings.Replace(s, old, new, 5 ))

     // 用 new 替换前 7 个匹配上的 old（实际没那么多）；n=7:  666666666666666666
    fmt.Println("n=7: ", strings.Replace(s, old, new, 7 ))
}