VScode shows an error when having multiple Go Projects in a directory

You probably have more than one go module in your workspace. If that is the case, you can change the go extension settings, in order to allow gopls to look for multiple modules in the workspace. Just add the following to your settings.json:

"gopls": {
    "experimentalWorkspaceModule": true,
}

You can read more about gopls configuration in the docs: https://github.com/golang/tools/blob/master/gopls/doc/settings.md