Example of a Async Blueprint HTTP Call.

BlueprintAsyncHTTP.cpp

// Fill out your copyright notice in the Description page of Project Settings.

#include "loginUserClient.h"
#include "ClientSDK.h"
#include "ClientSDKStructs.h"
#include "ConfigCacheIni.h"
#include "Misc/MessageDialog.h"
#include "Interfaces/IHttpResponse.h"
#include "HttpModule.h"
#include "Dom/JsonObject.h"
#include "Modules/ModuleManager.h"
#include "Serialization/JsonWriter.h"
#include "Serialization/JsonReader.h"
#include "Serialization/JsonSerializer.h"
#include "Policies/CondensedJsonPrintPolicy.h"
#include "Runtime/Core/Public/Containers/Array.h"
#include "Runtime/Core/Public/Internationalization/Text.h"
#include "Runtime/JsonUtilities/Public/JsonObjectConverter.h"

UloginUserClient* UloginUserClient::loginUserClient(FString user_email, FString user_password)
{
	UloginUserClient* HTTPQueryTask = NewObject<UloginUserClient>();

	HTTPQueryTask->Start(user_email, user_password);

	return HTTPQueryTask;
}

void UloginUserClient::Start(FString user_email, FString user_password)
{

	TSharedRef<IHttpRequest> HttpRequest = FHttpModule::Get().CreateRequest();
	HttpRequest->OnProcessRequestComplete().BindUObject(this, &UloginUserClient::HandleQuery);
	HttpRequest->SetURL(TEXT("https://localhost/")); //CHANGE THIS
	HttpRequest->SetVerb(TEXT("POST"));

	HttpRequest->SetHeader(TEXT("Content-Type"), TEXT("application/json; charset=utf-8"));

	TArray<FStringFormatArg> Args;
	Args.Add(FStringFormatArg(TEXT("Bearer")));
	FString UserSession;
	if (FParse::Value(FCommandLine::Get(), TEXT("-cslogin="), UserSession)) {
		Args.Add(FStringFormatArg(UserSession));
	} else {
		FMessageDialog::Open(EAppMsgType::Ok,TEXT("No Contact Systems User Session Found in Commandline Arguments."), TEXT("Contact Systems Error"));
	}
	FString Header = FString::Format(TEXT("{0} {1}"), Args);

	HttpRequest->SetHeader(TEXT("Authorization"), Header);
	TSharedPtr<FJsonObject> queryObject = MakeShareable(new FJsonObject);
	TSharedPtr<FJsonObject> inputObject = MakeShareable(new FJsonObject);
		
			
	TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject);
				
					
	JsonObject->SetStringField("email", user_email);
					
				
					
	JsonObject->SetStringField("password", user_password);
					
				
	inputObject->SetObjectField("input", JsonObject);
			
		


	queryObject->SetStringField("operationName", TEXT("loginUser"));
	queryObject->SetStringField("query", TEXT("mutation loginUser($input: LoginInput!) { loginUser(input: $input) { accessToken, expires, refreshToken } }"));
	queryObject->SetObjectField("variables", inputObject);

	FString OutputString;
	TSharedRef< TJsonWriter<> > Writer = TJsonWriterFactory<>::Create(&OutputString);
	FJsonSerializer::Serialize(queryObject.ToSharedRef(), Writer);

	HttpRequest->SetContentAsString(OutputString);

	HttpRequest->ProcessRequest();
}

void UloginUserClient::HandleQuery(FHttpRequestPtr HttpRequest, FHttpResponsePtr HttpResponse, bool bSucceeded)
{
	FLoginDataServer Data;
	if (bSucceeded)	{
		TSharedPtr<FJsonObject> JsonParsed;
		TSharedRef<TJsonReader<TCHAR>> JsonReader = TJsonReaderFactory<TCHAR>::Create(HttpResponse->GetContentAsString());
		if (FJsonSerializer::Deserialize(JsonReader, JsonParsed)) {
			if (!JsonParsed->HasField(TEXT("errors"))) {
				TSharedPtr<FJsonObject> DataParsed;
				if (JsonParsed->TryGetObjectField(TEXT("data"), DataParsed)) {
					TSharedPtr<FJsonObject> ObjParsed;
					if (DataParsed->TryGetObjectField("loginUser")) {
						if(FJsonObjectConverter::JsonObjectToUStruct(DataParsed, &Data, 0, 0)) {
				      OnSuccess.Broadcast(Data);
				    } else {
							OnFail.Broadcast(Data);
						}
					} else {
						OnFail.Broadcast(Data);
					}
				} else {
					OnFail.Broadcast(Data);
				}
			} else {
				OnFail.Broadcast(Data);
			}
		} else {
			OnFail.Broadcast(Data);
		}
	} else {
		OnFail.Broadcast(Data);
	}
}

BlueprintAsyncHTTP.h

#pragma once

#include "CoreMinimal.h"
#include "UObject/Object.h"
#include "UObject/WeakObjectPtr.h"
#include "Interfaces/IHttpRequest.h"
#include "Kismet/BlueprintAsyncActionBase.h"
#include "ClientSDKStructs.h"
#include "loginUserClient.generated.h"


DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FloginUserClientDelegate, FLoginDataClient&, Response);

/**
 *
 */
UCLASS()
class CLIENTSDK_API UloginUserClient : public UBlueprintAsyncActionBase
{
	GENERATED_BODY()
public:

	UFUNCTION(BlueprintCallable, meta = (BlueprintInternalUseOnly = "true", Keywords = "HTTP loginUserClient Query"), Category = "AsyncHTTP|API|Client")
		static UloginUserClient* loginUserClient(FString user_email, FString user_password);

public:

	UPROPERTY(BlueprintAssignable)
		FloginUserClientDelegate OnSuccess;

	UPROPERTY(BlueprintAssignable)
		FloginUserClientDelegate OnFail;

public:

	void Start(FString user_email, FString user_password);
private:

	/** Handles json requests coming from the web */
	void HandleQuery(FHttpRequestPtr HttpRequest, FHttpResponsePtr HttpResponse, bool bSucceeded);
};