client/operations.go
func (op *remoteOperation) AddHandler(function func(api.Operation)) (*EventTarget, error) {
	var err error
	var target *EventTarget

	// Attach to the existing target operation
	if op.targetOp != nil {
		target, err = op.targetOp.AddHandler(function)
		if err != nil {
			return nil, err
		}
	} else {
		// Generate a mock EventTarget
		target = &EventTarget{
			function: func(api.Event) { function(api.Operation{}) },
			types:    []string{"operation"},
		}
	}

	// Add the handler to our list
	op.handlers = append(op.handlers, function)

	return target, nil
}
func (op *remoteOperation) AddHandler(function func(api.Operation)) (*EventTarget, error) {
	var err error
	var target *EventTarget

	// Attach to the existing target operation
	if op.targetOp != nil {
		target, err = op.targetOp.AddHandler(function)
		if err != nil {
			return nil, err
		}
	} else {
		// Generate a mock EventTarget
		target = &EventTarget{
			function: func(api.Event) { function(api.Operation{}) },
			types:    []string{"operation"},
		}
	}

	// Add the handler to our list
	op.handlers = append(op.handlers, function)

	return target, nil
}
// AddHandler adds a function to be called whenever an event is received