JsonWriter.fs

open System
open System.IO
open System.Text.Json
open System.Threading.Tasks
open FSharp.Control.Tasks.V2

type MyRecord = {
    Name: string
    Age: int
    Id: Guid
}

let writeJson () =
    task {
        use stream = File.OpenWrite "data.json"

        let jwo = JsonWriterOptions(Indented = true)
        use writer = new Utf8JsonWriter(stream, jwo)
        writer.WriteStartArray()
        
        for i = 1 to 10_000_000 do
            let x = {
                Name = Guid.NewGuid().ToString()
                Age = 99
                Id = Guid.NewGuid()}
            JsonSerializer.Serialize(writer, x)
            if i % 1000 = 0 then
                do! writer.FlushAsync()
        
        writer.WriteEndArray()
        do! writer.FlushAsync()
    }

[<EntryPoint>]
let main argv =
    writeJson () |> Task.WaitAll
    0