RelaSphere/Assets/GameAssets/Scripts/Web/WebRequest.cs

using System;
using System.Collections;
using UnityEngine;
using UnityEngine.Networking;

public delegate void RequestDelegate(UnityWebRequest request, string data);

public static class WebRequest
{
    private static readonly string server = "http://localhost:3000/api/";

    public static void Get(MonoBehaviour behaviour, string url, RequestDelegate action)
    {
        behaviour.StartCoroutine(GetRequest(server+url, action));
    }

    public static void Post(MonoBehaviour behaviour, string url, string jsonData, RequestDelegate action)
    {
        behaviour.StartCoroutine(PostRequest(server + url, jsonData, action));
    }

    public static void PostFile(MonoBehaviour behaviour, string url, string filePath, RequestDelegate action)
    {
        behaviour.StartCoroutine(PostFileRequest(server + url, filePath, action));
    }

    private static IEnumerator GetRequest(string url, RequestDelegate action)
    {
        using (UnityWebRequest request = UnityWebRequest.Get(url))
        {
            request.SetRequestHeader("Content-Type", "application/json");
            yield return request.SendWebRequest();

            action(request, request.downloadHandler.text);
        }
    }

    private static IEnumerator PostRequest(string url, string jsonData, RequestDelegate action)
    {
        var request = new UnityWebRequest(url, "POST");
        byte[] bodyRaw = new System.Text.UTF8Encoding().GetBytes(jsonData);
        request.uploadHandler = new UploadHandlerRaw(bodyRaw);
        request.downloadHandler = new DownloadHandlerBuffer();
        request.SetRequestHeader("Content-Type", "application/json");

        yield return request.SendWebRequest();

        action(request, request.downloadHandler.text);
    }

    private static IEnumerator PostFileRequest(string url, string filePath, RequestDelegate action)
    {
        var request = new UnityWebRequest(url, "POST");
        request.uploadHandler = new UploadHandlerFile(filePath);
        request.downloadHandler = new DownloadHandlerBuffer();
        request.SetRequestHeader("Content-Type", "multipart/form-data");

        yield return request.SendWebRequest();

        action(request, request.downloadHandler.text);
    }

}