manager/dedup.go
func (d *DedupManager) createSession(client *consulapi.Client) {
START:
	log.Printf("[INFO] (dedup) attempting to create session")
	session := client.Session()
	sessionCh := make(chan struct{})
	ttl := fmt.Sprintf("%.6fs", float64(*d.config.TTL)/float64(time.Second))
	se := &consulapi.SessionEntry{
		Name:     "Consul-Template de-duplication",
		Behavior: "delete",
		TTL:      ttl,
	}
	id, _, err := session.Create(se, nil)
	if err != nil {
		log.Printf("[ERR] (dedup) failed to create session: %v", err)
		goto WAIT
	}
	log.Printf("[INFO] (dedup) created session %s", id)

	// Attempt to lock each template
	for _, t := range d.templates {
		d.wg.Add(1)
		go d.attemptLock(client, id, sessionCh, t)
	}

	// Renew our session periodically
	if err := session.RenewPeriodic("15s", id, nil, d.stopCh); err != nil {
		log.Printf("[ERR] (dedup) failed to renew session: %v", err)
	}
	close(sessionCh)
	d.wg.Wait()

WAIT:
	select {
	case <-time.After(sessionCreateRetry):
		goto START
	case <-d.stopCh:
		return
	}
}
func (d *DedupManager) createSession(client *consulapi.Client) {
START:
	log.Printf("[INFO] (dedup) attempting to create session")
	session := client.Session()
	sessionCh := make(chan struct{})
	ttl := fmt.Sprintf("%.6fs", float64(*d.config.TTL)/float64(time.Second))
	se := &consulapi.SessionEntry{
		Name:     "Consul-Template de-duplication",
		Behavior: "delete",
		TTL:      ttl,
	}
	id, _, err := session.Create(se, nil)
	if err != nil {
		log.Printf("[ERR] (dedup) failed to create session: %v", err)
		goto WAIT
	}
	log.Printf("[INFO] (dedup) created session %s", id)

	// Attempt to lock each template
	for _, t := range d.templates {
		d.wg.Add(1)
		go d.attemptLock(client, id, sessionCh, t)
	}

	// Renew our session periodically
	if err := session.RenewPeriodic("15s", id, nil, d.stopCh); err != nil {
		log.Printf("[ERR] (dedup) failed to renew session: %v", err)
	}
	close(sessionCh)
	d.wg.Wait()

WAIT:
	select {
	case <-time.After(sessionCreateRetry):
		goto START
	case <-d.stopCh:
		return
	}
}
// createSession is used to create and maintain a session to Consul