go :=声明变量的错误

package main

import "fmt"

func main() {
    var s []int
    str:=[]string
   for i:=0;i<3;i++{
      s = append(s,i)
      str=[]string{}
      fmt.Println(str)


   }
   fmt.Println(s[0])




}

// run

# command-line-arguments
.\t94.go:7:10: type []string is not an expression

编译完成，并显示退出代码 2