Example of using EitherT monad transformer with Future

EitherFuture.scala

import cats.implicits._
import cats.data.EitherT

import scala.concurrent.Future
import scala.concurrent.Await
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._

trait ServiceError
case object Timeout extends ServiceError

type EitherFuture[A] = EitherT[Future, ServiceError, A]

def callFirstService: EitherFuture[String] = {
  EitherT[Future, ServiceError, String](
    Future.successful(Right("Hello"))
  )
}

def callSecondService: EitherFuture[String] = {
  EitherT[Future, ServiceError, String](
    Future.successful(Right("World !"))
  )
}

val result1: EitherFuture[String] = callFirstService
val result2: EitherFuture[String] = callSecondService

val result = for {
  r1 <- result1
  r2 <- result2
} yield r1 + r2

Await.result(result.value, 1 seconds)