code: func (a *AddrManager) Attempt(addr *wire.NetAddress) {
  	a.mtx.Lock()
  	defer a.mtx.Unlock()
  
  	// find address.
  	// Surely address will be in tried by now?
  	ka := a.find(addr)
  	if ka == nil {
  		return
  	}
  	// set last tried time to now
  	ka.attempts++
  	ka.lastattempt = time.Now()
  }
docs: // Attempt increases the given address' attempt counter and updates
  // the last attempt time.