5.6 Go 상용 함수

https://golang.org/pkg/        //golang  

       ，                      len(str)
     ,                        r:=[]rune(str)
                                 n, err := strconv.Atoi("12")
                                 str = strconv.Itoa(12345)
      []byte                   var bytes = []byte("hello go")
[]byte                         str = string([]byte{97, 98, 99})
10     2, 8, 16   :              str = strconv.FormatInt(123, 2) // 2-> 8 , 16
                           strings.Contains("seafood", "foo") //true
                        strings.Count("ceheese", "e") //4
            (==         )  fmt.Println(strings.EqualFold("abc", "Abc")) // true
               index  ，      -1      strings.Index("NLT_abc", "abc") // 4
                index，     -1         strings.LastIndex("go golang", "go")
                 strings.Replace("go go hello", "go", "go   ", n) ，n             ，   n=-1       
         ，     ，                strings.Split("hello,wrold,ok", ",")
               : strings.ToLower("Go") // go strings.ToUpper("Go") // GO
             : strings.TrimSpace(" tn a lone gopher ntrn ")
                : strings.Trim("! hello! ", " !") 
              : strings.TrimLeft("! hello! ", " !")
              :strings.TrimRight("! hello! ", " !")
                : strings.HasPrefix("ftp://192.168.10.1", "ftp") 
                : strings.HasSuffix("NLT_abc.jpg", "abc") //false

package time
//time                ，         

package main

import (
    "fmt"
    "time"
)

func main() {
    //      
    now := time.Now()
    fmt.Printf("    ：%v
", now)
    fmt.Printf("      %T
", now)
    //  now         
    fmt.Printf("      =%v  =%v  =%v  =%v  =%v  =%v
", now.Year(), int(now.Month()), now.Day(), now.Hour(), now.Minute(), now.Second())

    //     ,      2006-01-02 15:04:05      
    fmt.Printf(now.Format("2006-01-02 15:04:05
"))

    //Unix    UnixNano  
    fmt.Printf("unix   =%v unixnano   =%v
", now.Unix(), now.UnixNano())
}

package main

import (
    "fmt"
    "strconv"
    "time"
)

//        
func test() {
    str := ""
    for i := 0; i < 100000; i++ {
        // int  string
        str += "oldboy" + strconv.Itoa(i)
    }
}

func main() {
    //         
    start := time.Now().Unix()
    test()
    //         
    end := time.Now().Unix()
    fmt.Printf("  test()  ，    %v 
", end-start)
}