How to handle json map in Golang? How to handle interface type conversion?

func GetMapValueByKey(key string, mapData map[string]interface{}) interface{} {
    value, ok := mapData[key]
    if ok {
        return value
    }
    return nil
}

var transferList = mapTool.GetMapValueByKey("token_transfers", result)
for _, transfer := range transferList.([]interface{}) {
    var block_timestamp = transfer.(map[string]interface{})["block_ts"]
    var quantity = transfer.(map[string]interface{})["quant"]
    var quantityDecimal = safemath.String_to_decimal(quantity.(string)).Div(safemath.String_to_decimal("1000000000000000000"))
    var quantityString = quantityDecimal.String()
    fmt.Println(block_timestamp, quantityString)
}

{
    "total": 2,
    "rangeTotal": 2,
    "contractInfo": {},
    "token_transfers": [
        {
            "transaction_id": "1cf69dca430c8b8ae3c3c24aa2bf8707477",
            "block_ts": 1640057784000,
            "from_address": "TSjRp2LTtuyVx9ygZ8KVSR",
            "to_address": "TKdQQuUnhA8Ak8D8w2YeWdj",
            "block": 36507755,
            "contract_address": "TFHMVstk3JZhS6YVKY",
            "quant": "100000000000000000000000",
            "confirmed": true,
            "contractRet": "SUCCESS",
            "finalResult": "SUCCESS",
            "revert": false,
            "tokenInfo": {
                "tokenId": "TFHMqKBygS6YVKY",
                "tokenAbbr": "ETH",
                "tokenName": "ETHCoin",
                "tokenDecimal": 18,
                "tokenCanShow": 1,
                "tokenType": "trc20",
                "tokenLogo": "https://coin.top/production/upload/logo/TFHMVstk3bZhLqKBygS6YVKY.png?t=1639808185156",
                "tokenLevel": "0",
                "issuerAddr": "TSjRp2Lx9ygZ8KxBUkG3YVSR",
                "vip": false
            },
            "fromAddressIsContract": false,
            "toAddressIsContract": false
        },
        {
            "transaction_id": "99e5a00674e96393b9add285f",
            "block_ts": 1640057766000,
            "from_address": "TSjRp2LTtugZ8KxBUkG3YVSR",
            "to_address": "TKdQiH76nhA8AkhR7xeWdj",
            "block": 36507749,
            "contract_address": "TFH1ygS6YVKY",
            "quant": "100000000000000000000000",
            "confirmed": true,
            "contractRet": "SUCCESS",
            "finalResult": "SUCCESS",
            "revert": false,
            "tokenInfo": {
                "tokenId": "TFHMWdTtkj1abZhLqKVKY",
                "tokenAbbr": "ETH",
                "tokenName": "ETHCoin",
                "tokenDecimal": 18,
                "tokenCanShow": 1,
                "tokenType": "trc20",
                "tokenLogo": "https://coin.top/production/upload/logo/TFHMgS6YVKY.png?t=1639808185156",
                "tokenLevel": "0",
                "issuerAddr": "TSjRp2LTtuyvGYYVSR",
                "vip": false
            },
            "fromAddressIsContract": false,
            "toAddressIsContract": false
        }
    ]
}

https://transform.tools/json-to-go 

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