What is environment path when call method in referenced project?

There two project in a solution which one of them is referenced another. Project 1: .NET Core MVC Project 2: .NET Core API

Both projects are docker enabled with Linux as OS.

Project 2 has Project 1 as referenced project.

A method for saving file on server is in Project 1, it is used for saving file in wwwroot/folder.

An API is in Project 2 for to be consumed outside.

When I call the API, referenced method will be called but the path for saving file raised an exception like as below:

Could not find a part of the path '/app/D:\dev\Project1\wwwroot\folder

Saving file method:

    StringBuilder xmlFilePath = new StringBuilder();

    using (var ms = new MemoryStream())
    using (var writer = XmlWriter.Create(ms, settings))
    {
        doc.Save(writer);
        var xmlString = Encoding.UTF8.GetString(ms.ToArray());

        var pathFolder = _configuration.GetSection("FilesUrl").Value;

        xmlFilePath.Append(
            Path.Combine(pathFolder, 
                         model.Domain.ToLower().Trim() + "-" + model.LanguageCode.ToLower().Trim() + "-file.xml"));
        using (var w = File.CreateText(xmlFilePath.ToString()))
        {
            await w.WriteLineAsync(xmlString);
        }
    }

Edit: I found that when project is running under Docker, Directory.GetCurrentDirectory() will set as /app, but changing project running under Kestrel or IIS will make it as common windows directory path.

What is wrong in my code? Why generated path contains "/app/"?