func DeleteMultiplelists() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/lists", host)
	request.Method = "DELETE"
	request.Body = []byte(` [
  1, 
  2, 
  3, 
  4
]`)
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
DeleteMultiplelists : Delete Multiple lists
DELETE /contactdb/lists
package main
import (
	"fmt"
	"log"
	"os"
	"github.com/sendgrid/sendgrid-go"
)
func CreateaCustomField() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/custom_fields", host)
	request.Method = "POST"
	request.Body = []byte(` {
  "name": "pet", 
  "type": "text"
}`)
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
func Retrieveallcustomfields() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/custom_fields", host)
	request.Method = "GET"
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
func RetrieveaCustomField() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/custom_fields/{custom_field_id}", host)
	request.Method = "GET"
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
func DeleteaCustomField() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/custom_fields/{custom_field_id}", host)
	request.Method = "DELETE"
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
func CreateaList() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/lists", host)
	request.Method = "POST"
	request.Body = []byte(` {
  "name": "your list name"
}`)
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}
func Retrievealllists() {
	apiKey := os.Getenv("SENDGRID_API_KEY")
	host := "https://api.sendgrid.com"
	request := sendgrid.GetRequest(apiKey, "/v3/contactdb/lists", host)
	request.Method = "GET"
	response, err := sendgrid.API(request)
	if err != nil {
		log.Println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
}