diff --git a/Makefile b/Makefile
index 31a66a9..58b7904 100644
--- a/Makefile
+++ b/Makefile
@@ -24,6 +24,7 @@ proto:
 .PHONY: lint
 lint:
 	@go-cleanarch
+	@./scripts/lint.sh common
 	@./scripts/lint.sh trainer
 	@./scripts/lint.sh trainings
 	@./scripts/lint.sh users
diff --git a/internal/common/client/grpc.go b/internal/common/client/grpc.go
index 391b8b0..c7ceea4 100644
--- a/internal/common/client/grpc.go
+++ b/internal/common/client/grpc.go
@@ -70,7 +70,8 @@ func grpcDialOpts(grpcAddr string) ([]grpc.DialOption, error) {
 		return nil, errors.Wrap(err, "cannot load root CA cert")
 	}
 	creds := credentials.NewTLS(&tls.Config{
-		RootCAs: systemRoots,
+		RootCAs:    systemRoots,
+		MinVersion: tls.VersionTLS12,
 	})
 
 	return []grpc.DialOption{
diff --git a/internal/common/server/http.go b/internal/common/server/http.go
index d11214b..a7ad1e3 100644
--- a/internal/common/server/http.go
+++ b/internal/common/server/http.go
@@ -31,7 +31,7 @@ func RunHTTPServerOnAddr(addr string, createHandler func(router chi.Router) http
 
 	logrus.Info("Starting HTTP server")
 
-	http.ListenAndServe(addr, rootRouter)
+	_ = http.ListenAndServe(addr, rootRouter)
 }
 
 func setMiddlewares(router *chi.Mux) {
diff --git a/internal/common/tests/clients.go b/internal/common/tests/clients.go
index 1e9b233..b98dead 100644
--- a/internal/common/tests/clients.go
+++ b/internal/common/tests/clients.go
@@ -49,6 +49,8 @@ func (c TrainerHTTPClient) MakeHourAvailable(t *testing.T, hour time.Time) int {
 		Hours: []time.Time{hour},
 	})
 	require.NoError(t, err)
+	require.NoError(t, response.Body.Close())
+
 	return response.StatusCode
 }
 
@@ -57,6 +59,8 @@ func (c TrainerHTTPClient) MakeHourUnavailable(t *testing.T, hour time.Time) {
 		Hours: []time.Time{hour},
 	})
 	require.NoError(t, err)
+	require.NoError(t, response.Body.Close())
+
 	require.Equal(t, http.StatusNoContent, response.StatusCode)
 }
 
@@ -113,6 +117,8 @@ func (c TrainingsHTTPClient) CreateTrainingShouldFail(t *testing.T, note string,
 		Time:  hour,
 	})
 	require.NoError(t, err)
+	require.NoError(t, response.Body.Close())
+
 	require.Equal(t, http.StatusInternalServerError, response.StatusCode)
 }
 
@@ -127,6 +133,8 @@ func (c TrainingsHTTPClient) GetTrainings(t *testing.T) trainings.Trainings {
 func (c TrainingsHTTPClient) CancelTraining(t *testing.T, trainingUUID string, expectedStatusCode int) {
 	response, err := c.client.CancelTraining(context.Background(), trainingUUID)
 	require.NoError(t, err)
+	require.NoError(t, response.Body.Close())
+
 	require.Equal(t, expectedStatusCode, response.StatusCode)
 }