在Golang中初始化2D切片

Question

我正在尝试在Golang中初始化2D幻灯片，切片的每个元素始终具有一行并且包含3列或4列。这是我到目前为止所拥有的

package main

import (
    "fmt"
)

type Element struct {
    rowNumber int
}

type Block [][]Element

func main() {
    totalRows := 100
    leftBlockRows := 1
    leftBlockColumns := 3
    middleBlockRows := 1
    middleBlockColumns := 4
    rightBlockRows := 1
    rightBlockColumns := 3
    grid := make([][]Block, totalRows)

    for i := 0; i < totalRows; i++ {
        leftBlock := make(Block, leftBlockRows, leftBlockColumns)
        for j := 1; j < leftBlockRows; j++ {
            leftBlock[j] = append(leftBlock[j], Element{rowNumber: i})
        }
        grid[i] = append(grid[i], leftBlock)

        middleBlock := make(Block, middleBlockRows, middleBlockColumns)
        for j := 1; j < middleBlockRows; j++ {
            middleBlock[j] = append(middleBlock[j], Element{rowNumber: i})
        }
        grid[i] = append(grid[i], middleBlock)

        rightBlock := make(Block, rightBlockRows, rightBlockColumns)
        for j := 1; j < rightBlockRows; j++ {
            rightBlock[j] = append(rightBlock[j], Element{rowNumber: i})
        }
        grid[i] = append(grid[i], rightBlock)
    }
    fmt.Println(grid[0])
}

总是打印出最后一张照片

[[[]] [[]] [[]]]

我希望切片grid具有Element的实例。但这似乎是空的。我在这里想念什么？