Wrote a simple logger.

pkg/logging/logger.go

@@ -0,0 +1,82 @@
+package logging
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+type Logger struct {
+	file io.WriteCloser
+	mut  sync.Mutex
+}
+
+func NewLogger(path string) (*Logger, error) {
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_APPEND|os.O_CREATE, os.ModeAppend)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to open log file")
+	}
+
+	return &Logger{file: f}, nil
+}
+
+func (l *Logger) Println(v ...interface{}) {
+	l.mut.Lock()
+
+	nowStr := time.Now().UTC().Format(time.RFC3339)
+
+	fmt.Fprintln(l.file, nowStr, v)
+
+	l.mut.Unlock()
+}
+
+func (l *Logger) Printf(format string, v ...interface{}) {
+	l.mut.Lock()
+
+	// Ensure a new line will be written
+	if !strings.HasSuffix(format, "\n") {
+		format += "\n"
+	}
+
+	nowStr := time.Now().UTC().Format(time.RFC3339)
+
+	fmt.Fprintf(l.file, nowStr+format, v...)
+
+	l.mut.Unlock()
+}
+
+func (l *Logger) Fatalln(v ...interface{}) {
+	l.mut.Lock()
+
+	nowStr := time.Now().UTC().Format(time.RFC3339)
+
+	fmt.Fprintln(l.file, nowStr, v)
+
+	l.file.Close()
+	os.Exit(1)
+}
+
+func (l *Logger) Fatalf(format string, v ...interface{}) {
+	l.mut.Lock()
+
+	// Ensure a new line will be written
+	if !strings.HasSuffix(format, "\n") {
+		format += "\n"
+	}
+
+	nowStr := time.Now().UTC().Format(time.RFC3339)
+
+	fmt.Fprintf(l.file, nowStr+format, v...)
+
+	l.file.Close()
+	os.Exit(1)
+}
+
+func (l *Logger) Close() error {
+	return l.file.Close()
+}