在golang中使用make方法创建2D数组时，我遇到问题“紧急：运行时错误：索引超出范围”

I am new in golang and try to learn with small examples.

So I am trying to create a 2D array and assign a value but I am stuck here can anyone help me. here is my code.

package main

import (
    "fmt"
)

func main() {
    fmt.Println("Hello, playground")

    letters := make([][]string,0,2)
    letters[0][0] = "a"
    letters[0][1] = "b"
    letters[1][0] = "c"
    letters[1][1] = "d"

    fmt.Println(letters)
}

I am getting error when I run this code

panic: runtime error: index out of range