`JsonSerializer` support for records

jsonserializerrecords.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net5.0</TargetFramework>
    <LangVersion>preview</LangVersion>
    <Nullable>enable</Nullable>
  </PropertyGroup>

</Project>

Program.cs

using System;
using System.Text.Json;

Forecast forecast = new(DateTime.Now, 40)
{
    Summary = "Hot!"
};

string forecastJson = JsonSerializer.Serialize<Forecast>(forecast);
Console.WriteLine(forecastJson);
Forecast? forecastObj = JsonSerializer.Deserialize<Forecast>(forecastJson);
Console.Write(forecastObj);

public record Forecast (DateTime Date, int TemperatureC)
{
    public string? Summary {get; init;}
};

Produces the following output:

rich@thundera jsonserializerrecords % dotnet run
{"Date":"2020-09-12T18:24:47.053821-07:00","TemperatureC":40,"Summary":"Hot!"}
Forecast { Date = 9/12/2020 6:24:47 PM, TemperatureC = 40, Summary = Hot! }