感谢Willeke，我们找到了答案。代码应该是：

if event.type == NSEvent.EventType.rightMouseUp {
        // Right button click
        let statusBarMenu = NSMenu()
        let item1 = NSMenuItem(title:"Quit", action:#selector(self.applicationQuit),keyEquivalent: "")
        item1.target = self

        statusBarMenu.addItem(item1)

        statusItem.menu = statusBarMenu
        statusItem.button?.performClick(nil)
        statusItem.menu = nil
    }

参考：What is alternative to NSStatusItem.popUpMenu?

class AppDelegate: NSObject, NSApplicationDelegate {
    private var menuBarIcon: NSStatusItem!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        createMenuBarIcon()
    }
}

// Dock Icon
extension AppDelegate {
    func createMenuBarIcon() {
        self.menuBarIcon = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
        
        self.menuBarIcon?.button?.toolTip = "FileBo"
        
        self.menuBarIcon?.button?.action = #selector(menuBarIconClicksAction(_:))
        self.menuBarIcon?.button?.sendAction(on: [.leftMouseUp, .rightMouseUp])
        self.menuBarIcon?.button?.target = self
        
        let icon = NSImage(named: "MenuBarAppIcon")
        icon?.size = .init(width: 20, height: 20)
        
        self.menuBarIcon?.button?.image = icon
    }
    
    func destroyMenuBarIcon() {
        self.menuBarIcon = nil
    }
}

// Dock Menu
extension AppDelegate {
    @IBAction func menuBarIconClicksAction(_ sender: AnyObject) {
        guard let event = NSApp.currentEvent else { return }
        
        if event.type == NSEvent.EventType.rightMouseUp {
            menuBarIcon.menu = dockContextMenu(NSApplication.shared)
            menuBarIcon.button?.performClick(nil)
            menuBarIcon.menu = nil
        } else {
            toggleMainWnd()
        }
    }
    
    func dockContextMenu(_ sender: NSApplication) -> NSMenu {
        let dockMenu = NSMenu()
        
        dockMenu.addItem( NSMenuItem(title: String(localized: "Show/Hide FileBo"), action: #selector(ToggleWndFileBo(_:)), keyEquivalent: "") )
        dockMenu.addItem( NSMenuItem(title: String(localized: "Quit FileBo") , action: #selector(QuitFileBo(_:)), keyEquivalent: "") )
        
        return dockMenu
    }
    
    @IBAction func QuitFileBo(_ sender: AnyObject) {
        NSApplication.shared.terminate(nil);
    }
    
    @IBAction func ToggleWndFileBo(_ sender: AnyObject) {
        toggleMainWnd()
    }
}