Example of using Tendermint HTTP client to subscribe for new block headers

client.go

package main

import (
	"context"
	"os"
	"os/signal"
	"syscall"

	"github.com/tendermint/tendermint/libs/log"

	tmclient "github.com/tendermint/tendermint/rpc/client"
	tmtypes "github.com/tendermint/tendermint/types"
)

func main() {
	logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout))

	client := tmclient.NewHTTP("tcp://localhost:26657", "/websocket")
	client.SetLogger(logger)
	err := client.Start()
	if err != nil {
		logger.Error("Failed to start a client", "err", err)
		os.Exit(1)
	}
	defer client.Stop()

	query := "tm.event = 'NewBlockHeader'"
	out, err := client.Subscribe(context.Background(), "test", query)
	if err != nil {
		logger.Error("Failed to subscribe to query", "err", err, "query", query)
		os.Exit(1)
	}

	quit := make(chan os.Signal, 1)
	signal.Notify(quit, os.Interrupt, syscall.SIGTERM)

	for {
		select {
		case result := <-out:
			logger.Info("got new block header",
				"height", result.Data.(tmtypes.EventDataNewBlockHeader).Header.Height)
		case <-quit:
			os.Exit(0)
		}
	}
}