Amazon Route53 JSON to a CSV in golang

dns2csv.go

package main

import (
	"encoding/csv"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"strconv"
)

type AWSjson struct {
	ResourceRecordSets []struct {
		ResourceRecords []struct {
			Value string `json:"Value"`
		} `json:"ResourceRecords"`
		Type []string `json:"Type"`
		Name []string `json:"Name"`
		TTL  int      `json:"TTL"`
	} `json:"ResourceRecordSets"`
}

func check(e error) {
	if e != nil {
		panic(e)
	}
}

//I took this from Go's blog, but I mostly understand it, below was my attempt
//sliceGrow := make([]string, len(WriteRow), (cap(WriteRow)+1+cap(valDat)*2))
func AppendString(slice []string, data []string) []string {
	m := len(slice)
	n := m + len(data)
	if n > cap(slice) {
		newSlice := make([]string, (n+1)*2) //I do not know why we double it
		copy(newSlice, slice)
		slice = newSlice
	}
	slice = slice[0:n] //I do not know why we need to specify the range til n
	copy(slice[m:n], data)
	return slice
}

/* I should make these functions, and this should work, but isn't
func mapify_string(mapper interface{}) {
	return mapper.(map[string]interface{})
}

func mapify_list(mapper interface{}) {
	return mapper.(map[]interface{})
}
*/

func main() {

	dat, err := ioutil.ReadFile("old_zone_file.json")
	check(err)
	f, erro := os.Create("/tmp/data.csv")
	check(erro)
	defer f.Close()

	csvWriter := csv.NewWriter(f)
	csvWriter.Write([]string{"Name", "Type", "TTL", "Value(s)"})

	var AmazonJson interface{}
	json.Unmarshal(dat, &AmazonJson)
	AmazonMapped := AmazonJson.(map[string]interface{})
	AmazonReMapped := AmazonMapped["ResourceRecordSets"].([]interface{})
	for _, obj := range AmazonReMapped {
		valDat := make([]string, 1)
		objMap, _ := obj.(map[string]interface{})
		csvName := objMap["Name"].(string)
		csvTTL := strconv.FormatFloat(objMap["TTL"].(float64), 'f', -1, 64)
		csvType := objMap["Type"].(string)
		WriteRow := []string{csvType, csvTTL, csvName}
		objList, _ := objMap["ResourceRecords"].([]interface{})
		for _, val := range objList {
			objValue, _ := val.(map[string]interface{})
			valDat = append(valDat, string(objValue["Value"].(string)))
			/*so many strings! this is due the fact that it returns a mapped object, the
			string method says I just want the string of the indexed reference instead
			of interface{}, the string func is correcting the assertation? still
			don't fully know :-( */
		}
		fmt.Println(net.LookupHost(csvName))
		WriteRow = AppendString(WriteRow, valDat)
		csvWriter.Write(WriteRow)
	}

}