package main
 
import (
    "fmt"
    "strings"
)
 
func main() {
    str := "Hello, World!"
 
    // 拼接字符串
    fmt.Println(strings.Join([]string{"Hello", "World"}, ", "))
 
    // 分割字符串
    splitStr := strings.Split(str, ",")
    fmt.Println(splitStr)
 
    // 替换字符串
    newStr := strings.Replace(str, "World", "Go", 1)
    fmt.Println(newStr)
 
    // 查找子串
    index := strings.Index(str, "World")
    fmt.Println(index)
}

package main
 
import (
    "fmt"
    "math"
)
 
func main() {
    num := 3.14
 
    // 向上取整
    ceil := math.Ceil(num)
    fmt.Println(ceil)
 
    // 向下取整
    floor := math.Floor(num)
    fmt.Println(floor)
 
    // 取平方根
    sqrt := math.Sqrt(num)
    fmt.Println(sqrt)
 
    // 求幂
    pow := math.Pow(num, 2)
    fmt.Println(pow)
}

package main
 
import (
    "fmt"
    "time"
)
 
func main() {
    // 获取当前时间
    now := time.Now()
    fmt.Println(now)
 
    // 格式化输出时间
    fmt.Println(now.Format("2006-01-02 15:04:05"))
 
    // 计算时间差
    oneYearAgo := now.AddDate(-1, 0, 0)
    diff := now.Sub(oneYearAgo)
    fmt.Println(diff.Hours())
}