Groupby evaulating locally for Entity Framework Core 2.1.4 inside Azure Function version 2

Microsoft says that the Entity Framework Core 2.1 generates a GROUPBY statement to the server. I have an Azure Function using the Entity Framework Core 2.1.4 but still got:

Microsoft.EntityFrameworkCore.Query:Warning: The LINQ expression 'Sum()' could not be translated and will be evaluated locally.

Microsoft.EntityFrameworkCore.Query:Warning: The LINQ expression 'Count()' could not be translated and will be evaluated locally.

My query is:

var q = await db.TblRainGauging5minutes
    .Where(x => x.G_ID == 1)
    .GroupBy(x => new { x.G_ID })
    .Select(g => new {
        Id = g.Key.G_ID,
        Total = g.Sum(v => v.R_Value ?? 0),
        Rows = g.Count()
    })
    .ToListAsync();

Here's my project setting:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
    <AzureFunctionsVersion>v2</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="AutoMapper.Extensions.ExpressionMapping" Version="2.0.0" />
    <PackageReference Include="AutoMapper.Extensions.Microsoft.DependencyInjection" Version="6.0.0" />
    <PackageReference Include="AzureFunctions.Autofac" Version="3.0.6" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.1.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="2.1.4" />
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="2.1.1" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="1.0.24" />
    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
  </ItemGroup>

Is anything wrong in my setting or code? Maybe it just doesn't work in Azure function 2? I have changed the target framework from netstandard2.0 to netcoreapp2.1.4 and I still get the problem.