get drand round number and timestamp in CSV format

drand_round.go

package main

import (
	"context"
	"encoding/csv"
	"encoding/hex"
	"fmt"
	"os"
	"strconv"
	"time"

	"github.com/drand/drand/chain"
	"github.com/drand/drand/client/http"
)

func main() {
	chainHash := "8990e7a9aaed2ffed73dbd7092123d6f289930540d7651336225dc172e51b2ce"
	hash, err := hex.DecodeString(chainHash)
	if err != nil {
		panic(fmt.Errorf("decoding chain hash: %w", err))
	}
	client, err := http.New("https://api.drand.sh/", hash, nil)
	if err != nil {
		panic(err)
	}
	info, err := client.Info(context.Background())
	if err != nil {
		panic(err)
	}
	records := []string{"round", "ts"}
	currentRound := chain.CurrentRound(time.Now().Unix(), info.Period, info.GenesisTime)
	w := csv.NewWriter(os.Stdout)
	w.Write(records)
	for n := 0; n < 10; n++ {
		round := currentRound - uint64(n)
		roundTime := chain.TimeOfRound(info.Period, info.GenesisTime, round)
		records = []string{strconv.Itoa(int(round)), strconv.Itoa(int(roundTime))}
		if err := w.Write(records); err != nil {
			panic(err)
		}
	}
	w.Flush()
	if err := w.Error(); err != nil {
		panic(err)
	}
}