Azure Function get SharePoint groups

postdata.json

{
    "groupName": "Flow Test Users",
    "siteUrl": "https://devtenant.sharepoint.com/sites/contoso"
}

project.json

{
  "frameworks": {
    "net46":{
      "dependencies": {
        "SharePointPnPCoreOnline": "2.17.1708.1"
      }
    }
   }
}

run.csx

#r "Newtonsoft.Json"
using System.Net;
using System.Collections.Generic;
using Microsoft.SharePoint.Client;
using System.Security;
using Newtonsoft.Json;

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log)
{
     dynamic data = await req.Content.ReadAsAsync<object>();
     string groupName = data.groupName;
     string siteUrl = data.siteUrl;
     List<SPUser> users = new List<SPUser>();
      log.Info("Querying site " + siteUrl + " for group " + groupName);

     using(ClientContext ctx = GetContext(siteUrl))
    {
        Web web = ctx.Web;
         Group sharepointGroup = web.SiteGroups.GetByName(groupName);  
         ctx.Load(web);  
         ctx.Load(sharepointGroup, grp => grp.Title, grp => grp.Users);  
         ctx.ExecuteQuery();  
         log.Info("Group has " + sharepointGroup.Users.Count + " users.");
          foreach(User usr in sharepointGroup.Users)  
          {  
             SPUser newUser = new SPUser()
             {
                DisplayName = usr.Title,
                Email = usr.Email             
             };
             users.Add(newUser);
          }  
    }
     return req.CreateResponse(HttpStatusCode.OK, JsonConvert.SerializeObject(users));
}

public static ClientContext GetContext(string siteUrl)
{
     ClientContext ctx = new ClientContext(siteUrl);
     ctx.Credentials = new SharePointOnlineCredentials("[email protected]", GetPassword("pass@word1"));
     return ctx;
}

private static SecureString GetPassword(string passwd)
{
    var secure = new SecureString();
    foreach (char c in passwd)
    {
       secure.AppendChar(c);
    }
     return secure;
}

public class SPUser
{
    public string DisplayName{ get; set;}
    public string Email { get; set;}

}