Print initialization errors to standard output

This way debugging configuration and initialization issues is simpler

config/config.go

@@ -88,12 +88,14 @@ func LoadConfig(configPath string) error {
 	file, err := os.Open(configPath)
 	if err != nil {
 		logger.Warn(logSender, "error loading configuration file: %v. Default configuration will be used: %+v", err, globalConf)
+		logger.WarnToConsole("error loading configuration file: %v. Default configuration will be used.", err)
 		return err
 	}
 	defer file.Close()
 	err = json.NewDecoder(file).Decode(&globalConf)
 	if err != nil {
-		logger.Warn(logSender, "error parsing config file: %v. Default configuration will be used: %+v", err, globalConf)
+		logger.Warn(logSender, "error parsing configuration file: %v. Default configuration will be used: %+v", err, globalConf)
+		logger.WarnToConsole("error parsing configuration file: %v. Default configuration will be used.", err)
 		return err
 	}
 	if strings.TrimSpace(globalConf.SFTPD.Banner) == "" {

logger/logger.go

@@ -1,6 +1,8 @@
 // Package logger provides logging capabilities.
 // It is a wrapper around zerolog for logging and lumberjack for log rotation.
-// It provides a request logger to log the HTTP requests for REST API too.
+// Logs are written to the specified log file.
+// Logging on the console is provided to print initialization info, errors and warnings.
+// The package provides a request logger to log the HTTP requests for REST API too.
 // The request logger uses chi.middleware.RequestLogger,
 // chi.middleware.LogFormatter and chi.middleware.LogEntry to build a structured
 // logger using zerlog
@@ -8,6 +10,7 @@ package logger
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/rs/zerolog"
 	lumberjack "gopkg.in/natefinch/lumberjack.v2"
@@ -19,6 +22,7 @@ const (
 
 var (
 	logger        zerolog.Logger
+	consoleLogger zerolog.Logger
 )
 
 // GetLogger get the configured logger instance
@@ -41,6 +45,13 @@ func InitLogger(logFilePath string, level zerolog.Level) {
 		MaxAge:     logMaxAge,
 		Compress:   false,
 	}).With().Timestamp().Logger().Level(level)
+
+	consoleOutput := zerolog.ConsoleWriter{
+		Out:        os.Stdout,
+		TimeFormat: dateFormat,
+		NoColor:    true,
+	}
+	consoleLogger = zerolog.New(consoleOutput).With().Timestamp().Logger()
 }
 
 // Debug logs at debug level for the specified sender
@@ -63,6 +74,26 @@ func Error(sender string, format string, v ...interface{}) {
 	logger.Error().Str("sender", sender).Msg(fmt.Sprintf(format, v...))
 }
 
+// DebugToConsole logs at debug level to stdout
+func DebugToConsole(format string, v ...interface{}) {
+	consoleLogger.Debug().Msg(fmt.Sprintf(format, v...))
+}
+
+// InfoToConsole logs at info level to stdout
+func InfoToConsole(format string, v ...interface{}) {
+	consoleLogger.Info().Msg(fmt.Sprintf(format, v...))
+}
+
+// WarnToConsole logs at info level to stdout
+func WarnToConsole(format string, v ...interface{}) {
+	consoleLogger.Warn().Msg(fmt.Sprintf(format, v...))
+}
+
+// ErrorToConsole logs at error level to stdout
+func ErrorToConsole(format string, v ...interface{}) {
+	consoleLogger.Error().Msg(fmt.Sprintf(format, v...))
+}
+
 // TransferLog logs an SFTP upload or download
 func TransferLog(operation string, path string, elapsed int64, size int64, user string, connectionID string) {
 	logger.Info().

main.go

@@ -45,7 +45,8 @@ func main() {
 
 	err := dataprovider.Initialize(providerConf, configDir)
 	if err != nil {
-		logger.Warn(logSender, "error initializing data provider: %v", err)
+		logger.Error(logSender, "error initializing data provider: %v", err)
+		logger.ErrorToConsole("error initializing data provider: %v", err)
 		os.Exit(1)
 	}
 
@@ -61,6 +62,7 @@ func main() {
 		logger.Debug(logSender, "initializing SFTP server with config %+v", sftpdConf)
 		if err := sftpdConf.Initialize(configDir); err != nil {
 			logger.Error(logSender, "could not start SFTP server: %v", err)
+			logger.ErrorToConsole("could not start SFTP server: %v", err)
 		}
 		shutdown <- true
 	}()
@@ -80,11 +82,13 @@ func main() {
 			}
 			if err := s.ListenAndServe(); err != nil {
 				logger.Error(logSender, "could not start HTTP server: %v", err)
+				logger.ErrorToConsole("could not start HTTP server: %v", err)
 			}
 			shutdown <- true
 		}()
 	} else {
 		logger.Debug(logSender, "HTTP server not started, disabled in config file")
+		logger.DebugToConsole("HTTP server not started, disabled in config file")
 	}
 
 	<-shutdown

sftpd/server.go

@@ -52,6 +52,7 @@ func (c Configuration) Initialize(configDir string) error {
 		utils.SetUmask(int(umask), c.Umask)
 	} else {
 		logger.Warn(logSender, "error reading umask, please fix your config file: %v", err)
+		logger.WarnToConsole("error reading umask, please fix your config file: %v", err)
 	}
 	actions = c.Actions
 	serverConfig := &ssh.ServerConfig{
@@ -78,6 +79,7 @@ func (c Configuration) Initialize(configDir string) error {
 
 	if _, err := os.Stat(filepath.Join(configDir, "id_rsa")); os.IsNotExist(err) {
 		logger.Info(logSender, "creating new private key for server")
+		logger.InfoToConsole("id_rsa does not exist, creating new private key for server")
 		if err := c.generatePrivateKey(configDir); err != nil {
 			return err
 		}