Hi Kathleen Sibo,
If you're locked out of your Surface Go and seeing a message that your password has expired, the first thing to check is whether your device is linked to a Microsoft Account. If it is, you can try resetting your password online by visiting account.microsoft.com. Once you've updated your password, your Surface Go should sync the new credentials provided it's connected to the internet and allow you to sign in again.
If that doesn't work or your device isn't connected to the internet, there are still a couple of options. You can create a USB recovery drive using another Windows PC and download the official recovery image for your Surface Go from Microsoft's Surface Recovery Image page. This will let you reset the device and regain access, though it will erase your data. Alternatively, if you have access to a Windows installation USB, you can boot into Command Prompt and create a new local administrator account to log in and back up your files before doing a full reset.
Let me know if you need help with any of these steps, happy to walk you through it.
Best,
Carl