moving error to new

io/io.go

@@ -1,24 +1,36 @@
 package ioutil
 
 import (
+	"errors"
 	"io"
 	"sync"
 )
 
+// SafeWriter is a thread-safe wrapper for io.Writer
 type SafeWriter struct {
-	writer io.Writer
-	mutex  sync.Mutex
+	writer io.Writer   // The underlying writer
+	mutex  *sync.Mutex // Mutex for ensuring thread-safety
 }
 
-func NewSafeWriter(writer io.Writer) *SafeWriter {
-	return &SafeWriter{
+// NewSafeWriter creates and returns a new SafeWriter
+func NewSafeWriter(writer io.Writer) (*SafeWriter, error) {
+	// Check if the provided writer is nil
+	if writer == nil {
+		return nil, errors.New("writer is nil")
+	}
+
+	safeWriter := &SafeWriter{
 		writer: writer,
+		mutex:  &sync.Mutex{},
 	}
+	return safeWriter, nil
 }
 
+// Write implements the io.Writer interface in a thread-safe manner
 func (sw *SafeWriter) Write(p []byte) (n int, err error) {
 	sw.mutex.Lock()
 	defer sw.mutex.Unlock()
+
 	if sw.writer == nil {
 		return 0, io.ErrClosedPipe
 	}

io/io_test.go

@@ -3,26 +3,23 @@ package ioutil
 import (
 	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 func TestSafeWriter(t *testing.T) {
 	t.Run("success", func(t *testing.T) {
 		var sb strings.Builder
-		sw := NewSafeWriter(&sb)
-		_, err := sw.Write([]byte("test"))
-		if err != nil {
-			t.Fatalf("expected no error, got %v", err)
-		}
-		if sb.String() != "test" {
-			t.Fatalf("expected 'test', got '%s'", sb.String())
-		}
+		sw, err := NewSafeWriter(&sb)
+		require.Nil(t, err)
+		_, err = sw.Write([]byte("test"))
+		require.Nil(t, err)
+		require.Equal(t, "test", sb.String())
 	})
 
 	t.Run("failure", func(t *testing.T) {
-		sw := NewSafeWriter(nil)
-		_, err := sw.Write([]byte("test"))
-		if err == nil {
-			t.Fatalf("expected error, got nil")
-		}
+		sw, err := NewSafeWriter(nil)
+		require.NotNil(t, err)
+		require.Nil(t, sw)
 	})
 }