code: func (circuit *CircuitBreaker) IsOpen() bool {
  	circuit.mutex.RLock()
  	o := circuit.forceOpen || circuit.open
  	circuit.mutex.RUnlock()
  
  	if o {
  		return true
  	}
  
  	if uint64(circuit.metrics.Requests().Sum(time.Now())) < getSettings(circuit.Name).RequestVolumeThreshold {
  		return false
  	}
  
  	if !circuit.metrics.IsHealthy(time.Now()) {
  		// too many failures, open the circuit
  		circuit.setOpen()
  		return true
  	}
  
  	return false
  }
docs: // IsOpen is called before any Command execution to check whether or
  // not it should be attempted. An "open" circuit means it is disabled.