diff --git a/build.sbt b/build.sbt
index d5a0c52d..654e6266 100644
--- a/build.sbt
+++ b/build.sbt
@@ -2,13 +2,13 @@ import sbt.Keys.libraryDependencies
 
 val logger: Logger = ConsoleLogger()
 
-crossScalaVersions := Seq("2.12.10")
+crossScalaVersions := Seq("2.12.10", "2.13.1")
 
 lazy val Versions = new {
   val gpb3Version = "3.11.1"
-  val grpcVersion = "1.26.0"
-  val circeVersion = "0.11.2"
-  val http4sVersion = "0.20.15"
+  val grpcVersion = "1.27.0"
+  val circeVersion = "0.13.0"
+  val http4sVersion = "0.21.1"
   val akkaHttp = "10.1.5" // DO NOT upgrade to 10.1.[67] - will cause https://github.com/scala/community-builds/issues/825
 }
 
@@ -110,8 +110,8 @@ lazy val core = (project in file("core")).settings(
     "io.grpc" % "grpc-core" % Versions.grpcVersion,
     "io.grpc" % "grpc-protobuf" % Versions.grpcVersion,
     "io.grpc" % "grpc-stub" % Versions.grpcVersion,
-    "org.typelevel" %% "cats-core" % "1.6.0",
-    "org.typelevel" %% "cats-effect" % "1.3.0",
+    "org.typelevel" %% "cats-core" % "2.1.1",
+    "org.typelevel" %% "cats-effect" % "2.1.1",
     "com.kailuowang" %% "mainecoon-core" % "0.6.4",
     "com.typesafe.scala-logging" %% "scala-logging" % "3.9.2",
     "org.slf4j" % "jul-to-slf4j" % "1.7.26",
@@ -176,5 +176,5 @@ def grpcExeFileName: String = {
 }
 
 val grpcArtifactId = "protoc-gen-grpc-java"
-val grpcExeUrl = url(s"http://repo1.maven.org/maven2/io/grpc/$grpcArtifactId/${Versions.grpcVersion}/$grpcExeFileName")
+val grpcExeUrl = url(s"https://repo1.maven.org/maven2/io/grpc/$grpcArtifactId/${Versions.grpcVersion}/$grpcExeFileName")
 val grpcExePath = SettingKey[xsbti.api.Lazy[File]]("grpcExePath")
diff --git a/core-scalapb/src/main/scala/com/avast/grpc/jsonbridge/scalapb/ScalaPBServiceHandlers.scala b/core-scalapb/src/main/scala/com/avast/grpc/jsonbridge/scalapb/ScalaPBServiceHandlers.scala
index 2ad6f77e..e93000bc 100644
--- a/core-scalapb/src/main/scala/com/avast/grpc/jsonbridge/scalapb/ScalaPBServiceHandlers.scala
+++ b/core-scalapb/src/main/scala/com/avast/grpc/jsonbridge/scalapb/ScalaPBServiceHandlers.scala
@@ -7,7 +7,7 @@ import cats.implicits._
 import com.avast.grpc.jsonbridge.GrpcJsonBridge.GrpcMethodName
 import com.avast.grpc.jsonbridge.ReflectionGrpcJsonBridge.{HandlerFunc, ServiceHandlers}
 import com.avast.grpc.jsonbridge.{BridgeError, JavaGenericHelper, ReflectionGrpcJsonBridge}
-import com.fasterxml.jackson.core.{JsonParseException, JsonProcessingException}
+import com.fasterxml.jackson.core.JsonProcessingException
 import com.typesafe.scalalogging.StrictLogging
 import io.grpc._
 import io.grpc.protobuf.ProtoFileDescriptorSupplier
@@ -22,7 +22,7 @@ import scala.util.control.NonFatal
 import scala.util.{Failure, Success}
 
 private[jsonbridge] object ScalaPBServiceHandlers extends ServiceHandlers with StrictLogging {
-  def createServiceHandlers[F[+ _]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
+  def createServiceHandlers[F[_]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
       implicit F: Async[F]): Map[GrpcMethodName, HandlerFunc[F]] = {
     if (ssd.getServiceDescriptor.getName == "grpc.reflection.v1alpha.ServerReflection") {
       logger.debug("Reflection endpoint service cannot be bridged because its implementation is not ScalaPB-based")
@@ -86,7 +86,7 @@ private[jsonbridge] object ScalaPBServiceHandlers extends ServiceHandlers with S
     Seq(servicePackage + "." + fileNameWithoutExtension + "." + serviceName + "Grpc$", servicePackage + "." + serviceName + "Grpc$")
   }
 
-  private def createHandler[F[+ _]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_])(method: ServerMethodDefinition[_, _])(
+  private def createHandler[F[_]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_])(method: ServerMethodDefinition[_, _])(
       implicit F: Async[F]): (GrpcMethodName, HandlerFunc[F]) = {
     val requestCompanion = getRequestCompanion(method)
     val requestClass = Class.forName(requestCompanion.getClass.getName.stripSuffix("$"))
@@ -144,7 +144,7 @@ private[jsonbridge] object ScalaPBServiceHandlers extends ServiceHandlers with S
     companionField.get(requestMarshaller).asInstanceOf[GeneratedMessageCompanion[_]]
   }
 
-  private def fromScalaFuture[F[+ _], A](ec: ExecutionContext)(fsf: F[Future[A]])(implicit F: Async[F]): F[A] = fsf.flatMap { sf =>
+  private def fromScalaFuture[F[_], A](ec: ExecutionContext)(fsf: F[Future[A]])(implicit F: Async[F]): F[A] = fsf.flatMap { sf =>
     F.async { cb =>
       sf.onComplete {
         case Success(r) => cb(Right(r))
diff --git a/core/src/main/scala/com/avast/grpc/jsonbridge/JavaServiceHandlers.scala b/core/src/main/scala/com/avast/grpc/jsonbridge/JavaServiceHandlers.scala
index abe1d7c8..cdf38441 100644
--- a/core/src/main/scala/com/avast/grpc/jsonbridge/JavaServiceHandlers.scala
+++ b/core/src/main/scala/com/avast/grpc/jsonbridge/JavaServiceHandlers.scala
@@ -25,7 +25,7 @@ private[jsonbridge] object JavaServiceHandlers extends ServiceHandlers with Stri
     JsonFormat.printer().includingDefaultValueFields().omittingInsignificantWhitespace()
   }
 
-  def createServiceHandlers[F[+ _]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
+  def createServiceHandlers[F[_]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
       implicit F: Async[F]): Map[GrpcMethodName, HandlerFunc[F]] = {
     val futureStubCtor = createFutureStubCtor(ssd.getServiceDescriptor, inProcessChannel)
     ssd.getMethods.asScala
@@ -42,7 +42,7 @@ private[jsonbridge] object JavaServiceHandlers extends ServiceHandlers with Stri
       method.invoke(null, inProcessChannel).asInstanceOf[AbstractStub[_]]
   }
 
-  private def createHandler[F[+ _]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_])(method: ServerMethodDefinition[_, _])(
+  private def createHandler[F[_]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_])(method: ServerMethodDefinition[_, _])(
       implicit F: Async[F]): (GrpcMethodName, HandlerFunc[F]) = {
     val requestMessagePrototype = getRequestMessagePrototype(method)
     val javaMethod = futureStubCtor().getClass
@@ -62,7 +62,7 @@ private[jsonbridge] object JavaServiceHandlers extends ServiceHandlers with Stri
     methodName.substring(0, 1).toLowerCase + methodName.substring(1)
   }
 
-  private def coreHandler[F[+ _]](requestMessagePrototype: Message, execute: (Message, Map[String, String]) => F[MessageOrBuilder])(
+  private def coreHandler[F[_]](requestMessagePrototype: Message, execute: (Message, Map[String, String]) => F[MessageOrBuilder])(
       implicit F: Async[F]): HandlerFunc[F] = { (json, headers) =>
     {
       parseRequest(json, requestMessagePrototype) match {
@@ -86,7 +86,7 @@ private[jsonbridge] object JavaServiceHandlers extends ServiceHandlers with Stri
     }
   }
 
-  private def executeRequest[F[+ _]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_], javaMethod: Method)(
+  private def executeRequest[F[_]](ec: ExecutionContext)(futureStubCtor: () => AbstractStub[_], javaMethod: Method)(
       req: Message,
       headers: Map[String, String])(implicit F: Async[F]): F[MessageOrBuilder] = {
     val metaData = {
@@ -107,7 +107,7 @@ private[jsonbridge] object JavaServiceHandlers extends ServiceHandlers with Stri
       requestBuilder.build()
     }
 
-  private def fromListenableFuture[F[+ _], A](ec: ExecutionContext)(flf: F[ListenableFuture[A]])(implicit F: Async[F]): F[A] = flf.flatMap {
+  private def fromListenableFuture[F[_], A](ec: ExecutionContext)(flf: F[ListenableFuture[A]])(implicit F: Async[F]): F[A] = flf.flatMap {
     lf =>
       F.async { cb =>
         Futures.addCallback(lf, new FutureCallback[A] {
diff --git a/core/src/main/scala/com/avast/grpc/jsonbridge/ReflectionGrpcJsonBridge.scala b/core/src/main/scala/com/avast/grpc/jsonbridge/ReflectionGrpcJsonBridge.scala
index 49e8818c..62130a0e 100644
--- a/core/src/main/scala/com/avast/grpc/jsonbridge/ReflectionGrpcJsonBridge.scala
+++ b/core/src/main/scala/com/avast/grpc/jsonbridge/ReflectionGrpcJsonBridge.scala
@@ -1,6 +1,7 @@
 package com.avast.grpc.jsonbridge
 
 import cats.effect._
+import cats.syntax.all._
 import com.avast.grpc.jsonbridge.GrpcJsonBridge.GrpcMethodName
 import com.avast.grpc.jsonbridge.ReflectionGrpcJsonBridge.{HandlerFunc, ServiceHandlers}
 import com.typesafe.scalalogging.StrictLogging
@@ -10,14 +11,14 @@ import io.grpc.inprocess.{InProcessChannelBuilder, InProcessServerBuilder}
 
 import scala.collection.JavaConverters._
 import scala.concurrent.ExecutionContext
-import scala.language.{existentials, higherKinds}
+import scala.language.higherKinds
 
 object ReflectionGrpcJsonBridge extends ReflectionGrpcJsonBridge(JavaServiceHandlers) {
   // JSON body and headers to a response (fail status or JSON response)
-  type HandlerFunc[F[+ _]] = (String, Map[String, String]) => F[Either[BridgeError.Narrow, String]]
+  type HandlerFunc[F[_]] = (String, Map[String, String]) => F[Either[BridgeError.Narrow, String]]
 
   trait ServiceHandlers {
-    def createServiceHandlers[F[+ _]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
+    def createServiceHandlers[F[_]](ec: ExecutionContext)(inProcessChannel: ManagedChannel)(ssd: ServerServiceDefinition)(
         implicit F: Async[F]): Map[GrpcMethodName, HandlerFunc[F]]
   }
 
@@ -26,11 +27,11 @@ object ReflectionGrpcJsonBridge extends ReflectionGrpcJsonBridge(JavaServiceHand
 
 private[jsonbridge] class ReflectionGrpcJsonBridge(serviceHandlers: ServiceHandlers) extends StrictLogging {
 
-  def createFromServer[F[+ _]](ec: ExecutionContext)(grpcServer: io.grpc.Server)(implicit F: Async[F]): Resource[F, GrpcJsonBridge[F]] = {
+  def createFromServer[F[_]](ec: ExecutionContext)(grpcServer: io.grpc.Server)(implicit F: Async[F]): Resource[F, GrpcJsonBridge[F]] = {
     createFromServices(ec)(grpcServer.getImmutableServices.asScala: _*)
   }
 
-  def createFromServices[F[+ _]](ec: ExecutionContext)(services: ServerServiceDefinition*)(
+  def createFromServices[F[_]](ec: ExecutionContext)(services: ServerServiceDefinition*)(
       implicit F: Async[F]): Resource[F, GrpcJsonBridge[F]] = {
     for {
       inProcessServiceName <- Resource.liftF(F.delay { s"ReflectionGrpcJsonBridge-${System.nanoTime()}" })
@@ -43,14 +44,14 @@ private[jsonbridge] class ReflectionGrpcJsonBridge(serviceHandlers: ServiceHandl
     } yield bridge
   }
 
-  def createFromHandlers[F[+ _]](handlersPerMethod: Map[GrpcMethodName, HandlerFunc[F]])(implicit F: Async[F]): GrpcJsonBridge[F] = {
+  def createFromHandlers[F[_]](handlersPerMethod: Map[GrpcMethodName, HandlerFunc[F]])(implicit F: Async[F]): GrpcJsonBridge[F] = {
     new GrpcJsonBridge[F] {
 
       override def invoke(methodName: GrpcJsonBridge.GrpcMethodName,
                           body: String,
                           headers: Map[String, String]): F[Either[BridgeError, String]] =
         handlersPerMethod.get(methodName) match {
-          case Some(handler) => handler(body, headers)
+          case Some(handler) => handler(body, headers).map(x => x: Either[BridgeError, String])
           case None => F.pure(Left(BridgeError.GrpcMethodNotFound))
         }
 
@@ -62,7 +63,7 @@ private[jsonbridge] class ReflectionGrpcJsonBridge(serviceHandlers: ServiceHandl
     }
   }
 
-  private def createInProcessServer[F[+ _]](ec: ExecutionContext)(inProcessServiceName: String, services: Seq[ServerServiceDefinition])(
+  private def createInProcessServer[F[_]](ec: ExecutionContext)(inProcessServiceName: String, services: Seq[ServerServiceDefinition])(
       implicit F: Sync[F]): Resource[F, Server] =
     Resource {
       F.delay {
@@ -73,12 +74,12 @@ private[jsonbridge] class ReflectionGrpcJsonBridge(serviceHandlers: ServiceHandl
       }
     }
 
-  private def createInProcessChannel[F[+ _]](ec: ExecutionContext)(inProcessServiceName: String)(
+  private def createInProcessChannel[F[_]](ec: ExecutionContext)(inProcessServiceName: String)(
       implicit F: Sync[F]): Resource[F, ManagedChannel] =
     Resource[F, ManagedChannel] {
       F.delay {
         val c = InProcessChannelBuilder.forName(inProcessServiceName).executor(ec.execute(_)).build()
-        (c, F.delay { c.shutdown() })
+        (c, F.delay { val _ = c.shutdown() })
       }
     }
 
diff --git a/http4s/src/main/scala/com/avast/grpc/jsonbridge/http4s/Http4s.scala b/http4s/src/main/scala/com/avast/grpc/jsonbridge/http4s/Http4s.scala
index f591f10a..b074c9d0 100644
--- a/http4s/src/main/scala/com/avast/grpc/jsonbridge/http4s/Http4s.scala
+++ b/http4s/src/main/scala/com/avast/grpc/jsonbridge/http4s/Http4s.scala
@@ -1,9 +1,9 @@
 package com.avast.grpc.jsonbridge.http4s
 
-import cats.Applicative
 import cats.data.NonEmptyList
 import cats.effect._
 import cats.syntax.all._
+import cats._
 import com.avast.grpc.jsonbridge.GrpcJsonBridge.GrpcMethodName
 import com.avast.grpc.jsonbridge.{BridgeError, BridgeErrorResponse, GrpcJsonBridge}
 import com.typesafe.scalalogging.LazyLogging
@@ -15,7 +15,7 @@ import org.http4s.dsl.Http4sDsl
 import org.http4s.dsl.impl.EntityResponseGenerator
 import org.http4s.headers.{`Content-Type`, `WWW-Authenticate`}
 import org.http4s.server.middleware.{CORS, CORSConfig}
-import org.http4s.{Challenge, EntityEncoder, Header, Headers, HttpRoutes, MediaType, Response, Status}
+import org.http4s._
 
 import scala.language.{higherKinds, implicitConversions}
 
@@ -108,6 +108,10 @@ object Http4s extends LazyLogging {
 
   private def mapStatus[F[_]: Sync](s: GrpcStatus, configuration: Configuration)(implicit h: Http4sDsl[F]): F[Response[F]] = {
     import h._
+    val ClientClosedRequest = Status(499, "Client Closed Request")
+    final case class ClientClosedRequestOps(status: ClientClosedRequest.type) extends EntityResponseGenerator[F, F] {
+      val liftG: F ~> F = h.liftG
+    }
 
     val description = BridgeErrorResponse.fromGrpcStatus(s)
 
@@ -133,9 +137,6 @@ object Http4s extends LazyLogging {
     }
   }
 
-  val ClientClosedRequest = Status(499, "Client Closed Request")
-  final case class ClientClosedRequestOps[F[_], G[_]](status: ClientClosedRequest.type) extends AnyVal with EntityResponseGenerator[F, G]
-
   private implicit def grpcStatusJsonEntityEncoder[F[_]: Applicative]: EntityEncoder[F, BridgeErrorResponse] =
     jsonEncoderOf[F, BridgeErrorResponse]
 }
diff --git a/project/build.properties b/project/build.properties
index c0bab049..a919a9b5 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.2.8
+sbt.version=1.3.8