Golang 如何判断数组某个元素是否存在 (isset)

package main 
import (
 "fmt"
 "os"
)
 
func main() {
 if os.Args[1] != "" {
  fmt.Println("aaa")
 } else {
  fmt.Println("bbb")
 } 
}

panic: runtime error: index out of range
 
Goroutine 1 [running]:
main.main()
 /root/workspace/go/testn.go:9 +0x100
exit status 2

package main 
import (
 "fmt"
 "os"
)
 
func main() {
 var target string                             // 用来获取最终需要的os.Args[1]
 for k, v := range(os.Args) {
  if k == 1 {                               // 假设需要获取os.Args[k], k = 1
   target = v
  }
 } 
 
 if target != "" {                             // 不为空则表示os.Arg[1]存在
  fmt.Printf("os.Arg[1] = %s", target)     
 }
}

package main 
import (
 "fmt"
 "regexp"
) 

func main() { 
    //pattern := "\\d+"     //反斜杠要转义
 pattern := "[a-zA-Z]"   //匹配字母
 str := "a1.22.35.4"
 result, _ := regexp.MatchString(pattern, str)
 fmt.Println(result)   //true
}

package main 
import "fmt" 
import "GitHub.com/wxnacy/wgo/arrays" 
//go get github.com/wxnacy/wgo/arrays   安装包 

func main() {
 str := "342"
 var numbers []string
 numbers = append(numbers, "3332", "342", "ssDDD", "ssss", "%%%%") 
 index := arrays.ContainsString(numbers, str)
 if index == -1 {
  fmt.Printf("not exists") //-1说明不存在
 } else {
  fmt.Println(index) //存在则会返回元素的下标 
 }
}