add

trading_assistant_api/common/logger/logger.go

@@ -0,0 +1,32 @@
+package logger
+
+import (
+	"log"
+	"os"
+)
+
+type Logger interface {
+	Printf(format string, v ...any)
+	Fatalf(format string, v ...any)
+}
+
+type stdLogger struct {
+	l *log.Logger
+}
+
+func (s *stdLogger) Printf(format string, v ...any) { s.l.Printf(format, v...) }
+func (s *stdLogger) Fatalf(format string, v ...any) { s.l.Fatalf(format, v...) }
+
+var defaultLogger Logger = &stdLogger{
+	l: log.New(os.Stdout, "[app] ", log.LstdFlags|log.Lshortfile),
+}
+
+func L() Logger {
+	return defaultLogger
+}
+
+func SetLogger(l Logger) {
+	if l != nil {
+		defaultLogger = l
+	}
+}