Blocking calls for changes in consul

main.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"time"

	consulapi "github.com/hashicorp/consul/api"
)

func main() {
	c, err := consulapi.NewClient(consulapi.DefaultConfig())
	if err != nil {
		log.Panicln("Error creating consul client", err)
	}
	kv := c.KV()
	ch := make(chan string)
	go subscribeToChanges("loglevel", ch, kv)
	go func() {
		for data := range ch {
			log.Println("Detected key change:", data)
		}
	}()
	reader := bufio.NewReader(os.Stdin)
	fmt.Println("Press ENTER to exit…")
	reader.ReadString('\n')
}
func subscribeToChanges(key string, ch chan string, kv *consulapi.KV) {
	currentIndex := uint64(0)
	for {
		pair, meta, err := kv.Get(key, &consulapi.QueryOptions{
			WaitIndex: currentIndex,
		})
		if err != nil {
			log.Panicln("Error read from KV", err.Error(), err)
		}
		if pair == nil || meta == nil {
			// Query won’t be blocked if key not found
			time.Sleep(1 * time.Second)
		} else {
			ch <- string(pair.Value)
			currentIndex = meta.LastIndex
		}
	}
}