The computer is stuck in the "Undo Changes made to the computer" interface, which is a common problem after the Windows update fails. It is usually caused by the stuck rollback process and cannot enter the system normally. 1. First of all, you should wait patiently for a long enough time, especially after restarting, it may take more than 30 minutes to complete the rollback, and observe the hard disk light to determine whether it is still running. 2. If there is no progress for a long time, you can force shut down and enter the recovery environment (WinRE) multiple times, and try to start repair or system restore. 3. After entering safe mode, you can uninstall the most recent update records through the control panel. 4. Use the command prompt to execute the bootrec command in the recovery environment to repair the boot file, or run sfc/scannow to check the system file. 5. The last method is to use the "Reset this computer" function

When encountering the "RPCserverisunavailable" problem, first confirm whether it is a local service exception or a network configuration problem. 1. Check and start the RPC service to ensure that its startup type is automatic. If it cannot be started, check the event log; 2. Check the network connection and firewall settings, test the firewall to turn off the firewall, check DNS resolution and network connectivity; 3. Run the sfc/scannow and DISM commands to repair the system files; 4. Check the group policy and domain controller status in the domain environment, and contact the IT department to assist in the processing. Gradually check it in sequence to locate and solve the problem.

When you encounter the "DefaultGatewayisNotAvailable" prompt, it means that the computer cannot connect to the router or does not obtain the network address correctly. 1. First, restart the router and computer, wait for the router to fully start before trying to connect; 2. Check whether the IP address is set to automatically obtain, enter the network attribute to ensure that "Automatically obtain IP address" and "Automatically obtain DNS server address" are selected; 3. Run ipconfig/release and ipconfig/renew through the command prompt to release and re-acquire the IP address, and execute the netsh command to reset the network components if necessary; 4. Check the wireless network card driver, update or reinstall the driver to ensure that it works normally.

If the second monitor is not recognized by Windows, first check whether the cable and interface are normal, try to replace the HDMI, DP or VGA cable, confirm the plug-in video output port, and test different interfaces to eliminate compatibility issues; then verify the monitor power and input source settings, and connect the monitor separately to test whether it can be recognized; then enter the Windows display settings and click the "Detection" button, or use Win P to switch the display mode, and update the graphics card driver at the same time; finally check the graphics card specifications to confirm whether it supports multi-screen output to avoid exceeding its maximum output capability.

When encountering the "SYSTEM_SERVICE_EXCEPTION" blue screen error, you do not need to reinstall the system or replace the hardware immediately. You can follow the following steps to check: 1. Update or roll back hardware drivers such as graphics cards, especially recently updated drivers; 2. Uninstall third-party antivirus software or system tools, and use WindowsDefender or well-known brand products to replace them; 3. Run sfc/scannow and DISM commands as administrator to repair system files; 4. Check memory problems, restore the default frequency and re-plug and unplug the memory stick, and use Windows memory diagnostic tools to detect. In most cases, the driver and software problems can be solved first.

sync.WaitGroup is used to wait for a group of goroutines to complete the task. Its core is to work together through three methods: Add, Done, and Wait. 1.Add(n) Set the number of goroutines to wait; 2.Done() is called at the end of each goroutine, and the count is reduced by one; 3.Wait() blocks the main coroutine until all tasks are completed. When using it, please note: Add should be called outside the goroutine, avoid duplicate Wait, and be sure to ensure that Don is called. It is recommended to use it with defer. It is common in concurrent crawling of web pages, batch data processing and other scenarios, and can effectively control the concurrency process.

When Windows cannot detect a second monitor, first check whether the physical connection is normal, including power supply, cable plug-in and interface compatibility, and try to replace the cable or adapter; secondly, update or reinstall the graphics card driver through the Device Manager, and roll back the driver version if necessary; then manually click "Detection" in the display settings to identify the monitor to confirm whether it is correctly identified by the system; finally check whether the monitor input source is switched to the corresponding interface, and confirm whether the graphics card output port connected to the cable is correct. Following the above steps to check in turn, most dual-screen recognition problems can usually be solved.

The key to installing Go is to select the correct version, configure environment variables, and verify the installation. 1. Go to the official website to download the installation package of the corresponding system. Windows uses .msi files, macOS uses .pkg files, Linux uses .tar.gz files and unzip them to /usr/local directory; 2. Configure environment variables, edit ~/.bashrc or ~/.zshrc in Linux/macOS to add PATH and GOPATH, and Windows set PATH to Go in the system properties; 3. Use the government command to verify the installation, and run the test program hello.go to confirm that the compilation and execution are normal. PATH settings and loops throughout the process