public static class HostingEnvironmentExtensions
    {
        public static void Initialize(this IHostingEnvironment hostingEnvironment, string contentRootPath, WebHostOptions options)
        {
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }
            if (string.IsNullOrEmpty(contentRootPath))
            {
                throw new ArgumentException("A valid non-empty content root must be provided.", nameof(contentRootPath));
            }
            if (!Directory.Exists(contentRootPath))
            {
                throw new ArgumentException($"The content root '{contentRootPath}' does not exist.", nameof(contentRootPath));
            }

            hostingEnvironment.ApplicationName = options.ApplicationName;
            hostingEnvironment.ContentRootPath = contentRootPath;
            hostingEnvironment.ContentRootFileProvider = new PhysicalFileProvider(hostingEnvironment.ContentRootPath);

            var webRoot = options.WebRoot;
            if (webRoot == null)
            {
                // Default to /wwwroot if it exists.
                var wwwroot = Path.Combine(hostingEnvironment.ContentRootPath, "wwwroot");
                if (Directory.Exists(wwwroot))
                {
                    hostingEnvironment.WebRootPath = wwwroot;
                }
            }

.....

}