code: func (c *conn) MarkAsDead() {
  	c.Lock()
  	c.dead = true
  	if c.deadSince == nil {
  		utcNow := time.Now().UTC()
  		c.deadSince = &utcNow
  	}
  	c.failures += 1
  	c.Unlock()
  }
docs: // MarkAsDead marks this connection as dead, increments the failures
  // counter and stores the current time in dead since.