Fix: Close log file in Builder.Close() to prevent resource leak

Added proper cleanup of the log file opened in buildLogger() to prevent
file descriptor leaks in long-running deployments. The Close() method now
properly closes both the log file and RabbitMQ connections.

Changes:
- Added nil-safe log file closure in Builder.Close() method
- Added comprehensive unit tests to verify log file is properly closed
- Tests cover normal case, nil log file, and builder without log file

Author: AndreaBozzo

builder/builder.go

@@ -78,6 +78,14 @@ func (b *Builder) buildRabbitMQ(rabbitMQURI string) error {
 }
 
 func (b *Builder) Close() error {
+	// Close log file if it was opened
+	if b.logsFile != nil {
+		if err := b.logsFile.Close(); err != nil {
+			return err
+		}
+	}
+
+	// Close RabbitMQ connections
 	if b.rabbitMQConnection != nil {
 		if err := b.rabbitMQChannel.Close(); err != nil {
 			return err

builder/builder_test.go

@@ -0,0 +1,65 @@
+package builder
+
+import (
+	"os"
+	"testing"
+
+	"github.com/mariocandela/beelzebub/v3/parser"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuilderClose_LogFile(t *testing.T) {
+	// Create a temporary directory for the test
+	tmpDir := t.TempDir()
+	logFilePath := tmpDir + "/test.log"
+
+	// Create a builder instance
+	builder := NewBuilder()
+
+	// Build logger which opens a log file
+	loggingConfig := parser.Logging{
+		Debug:               false,
+		DebugReportCaller:   false,
+		LogDisableTimestamp: true,
+		LogsPath:            logFilePath,
+	}
+
+	err := builder.buildLogger(loggingConfig)
+	assert.NoError(t, err)
+	assert.NotNil(t, builder.logsFile)
+
+	// Verify the log file exists and is open
+	fileInfo, err := os.Stat(logFilePath)
+	assert.NoError(t, err)
+	assert.NotNil(t, fileInfo)
+
+	// Close the builder
+	err = builder.Close()
+	assert.NoError(t, err)
+
+	// Verify the log file is closed by attempting to write to it
+	// Writing to a closed file should return an error
+	_, err = builder.logsFile.WriteString("test")
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "file already closed")
+}
+
+func TestBuilderClose_NoLogFile(t *testing.T) {
+	// Create a builder without opening a log file
+	builder := NewBuilder()
+
+	// Close should succeed even without a log file
+	err := builder.Close()
+	assert.NoError(t, err)
+}
+
+func TestBuilderClose_NilLogFile(t *testing.T) {
+	// Create a builder with explicitly nil log file
+	builder := &Builder{
+		logsFile: nil,
+	}
+
+	// Close should succeed with nil log file
+	err := builder.Close()
+	assert.NoError(t, err)
+}