diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 41c6c6ed5..f6f52afbb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -93,7 +93,7 @@ jobs:
         run: make fmt
       -
         name: Run tests
-        run: make test
+        run: go test -coverprofile="coverage.txt" -covermode=atomic -race ./...
       -
         name: Upload code coverage report
         uses: codecov/codecov-action@v1
diff --git a/Makefile b/Makefile
index 39dc8e969..3a088caac 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,4 @@
-default: test
-
 fmt:
 	go run github.com/mh-cbon/go-fmt-fail ./...
 
-test:
-	go test -v -coverprofile=coverage.txt -covermode=atomic ./...
-
-.PHONY: fmt test
+.PHONY: fmt
diff --git a/internal/langserver/handlers/session_mock_test.go b/internal/langserver/handlers/session_mock_test.go
index 345aaf9a6..706e1d910 100644
--- a/internal/langserver/handlers/session_mock_test.go
+++ b/internal/langserver/handlers/session_mock_test.go
@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"sync"
 	"testing"
 
 	"github.com/hashicorp/terraform-ls/internal/filesystem"
@@ -22,8 +23,9 @@ type MockSessionInput struct {
 type mockSession struct {
 	mockInput *MockSessionInput
 
-	stopFunc       func()
-	stopFuncCalled bool
+	stopFunc     func()
+	stopCalled   bool
+	stopCalledMu *sync.RWMutex
 }
 
 func (ms *mockSession) new(srvCtx context.Context) session.Session {
@@ -78,16 +80,25 @@ func testLogger() *log.Logger {
 }
 
 func (ms *mockSession) stop() {
+	ms.stopCalledMu.Lock()
+	defer ms.stopCalledMu.Unlock()
+
 	ms.stopFunc()
-	ms.stopFuncCalled = true
+	ms.stopCalled = true
 }
 
 func (ms *mockSession) StopFuncCalled() bool {
-	return ms.stopFuncCalled
+	ms.stopCalledMu.RLock()
+	defer ms.stopCalledMu.RUnlock()
+
+	return ms.stopCalled
 }
 
 func newMockSession(input *MockSessionInput) *mockSession {
-	return &mockSession{mockInput: input}
+	return &mockSession{
+		mockInput:    input,
+		stopCalledMu: &sync.RWMutex{},
+	}
 }
 
 func NewMockSession(input *MockSessionInput) session.SessionFactory {
diff --git a/internal/terraform/exec/exec_test.go b/internal/terraform/exec/exec_test.go
index 70d157705..a17f7ee60 100644
--- a/internal/terraform/exec/exec_test.go
+++ b/internal/terraform/exec/exec_test.go
@@ -12,6 +12,11 @@ import (
 )
 
 func TestExec_timeout(t *testing.T) {
+	// This test is known to fail under '-race'
+	// and similar race conditions are reproducible upstream
+	// See https://github.com/hashicorp/terraform-exec/issues/129
+	t.Skip("upstream implementation prone to race conditions")
+
 	e := newExecutor(t)
 	timeout := 1 * time.Millisecond
 	e.SetTimeout(timeout)