FS2 + RabbitMQ

import java.util.concurrent.Executors
import cats.effect.{Blocker, ExitCode, IO, IOApp, Resource, Sync}
import dev.profunktor.fs2rabbit.config.Fs2RabbitConfig
import dev.profunktor.fs2rabbit.interpreter.RabbitClient
import dev.profunktor.fs2rabbit.model.{ExchangeName, RoutingKey}

object Demo extends IOApp {

  val config: Fs2RabbitConfig = Fs2RabbitConfig(
    virtualHost = "/",
    host = "127.0.0.1",
    username = Some("guest"),
    password = Some("guest"),
    port = 5672,
    ssl = false,
    connectionTimeout = 3,
    requeueOnNack = false,
    internalQueueSize = Some(500)
  )

  val blockerResource: Resource[IO, Blocker] =
    Resource
      .make(IO(Executors.newCachedThreadPool()))(es => IO(es.shutdown()))
      .map(Blocker.liftExecutorService)

  override def run(args: List[String]): IO[ExitCode] = {
    import cats.syntax.functor.toFunctorOps

    blockerResource.use { blocker =>
      RabbitClient[IO](config, blocker).flatMap { client =>
        Program.foo[IO](client).as(ExitCode.Success)
      }
    }
  }
}

object Program {
  import cats.syntax.flatMap.toFlatMapOps

  def foo[F[_]: Sync](client: RabbitClient[F]): F[Unit] = {
    client.createConnectionChannel.use { implicit channel =>
      client.createPublisher(ExchangeName("test"), RoutingKey("")).flatMap { publish =>
        publish("Hello")
      }
    }
  }
}