Add log Format option

debug/log/log.go

@@ -10,6 +10,8 @@ var (
 	DefaultSize = 1024
 	// DefaultLog logger
 	DefaultLog = NewLog()
+	// Default formatter
+	DefaultFormat = func(r Record) string { return r.Message.(string) }
 )
 
 // Log is debug log interface for reading and writing logs
@@ -37,3 +39,6 @@ type Stream interface {
 	Chan() <-chan Record
 	Stop() error
 }
+
+// Format is a function which formats the output
+type FormatFunc func(Record) string

debug/log/options.go

@@ -11,6 +11,8 @@ type Options struct {
 	Name string
 	// Size is the size of ring buffer
 	Size int
+	// Format specifies the output format
+	Format FormatFunc
 }
 
 // Name of the log
@@ -27,6 +29,12 @@ func Size(s int) Option {
 	}
 }
 
+func Format(f FormatFunc) Option {
+	return func(o *Options) {
+		o.Format = f
+	}
+}
+
 // DefaultOptions returns default options
 func DefaultOptions() Options {
 	return Options{

debug/log/os.go

@@ -15,7 +15,8 @@ import (
 
 // Should stream from OS
 type osLog struct {
-	once sync.Once
+	format FormatFunc
+	once   sync.Once
 
 	sync.RWMutex
 	buffer *ring.Buffer
@@ -140,8 +141,9 @@ func (o *osLog) Write(r Record) error {
 		go o.run()
 	})
 
-	b, _ := json.Marshal(r)
-	_, err := os.Stderr.Write(append(b, byte('\n')))
+	// generate output
+	out := o.format(r) + "\n"
+	_, err := os.Stderr.Write([]byte(out))
 	return err
 }
 
@@ -181,7 +183,15 @@ func (o *osStream) Stop() error {
 }
 
 func NewLog(opts ...Option) Log {
+	options := Options{
+		Format: DefaultFormat,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+
 	l := &osLog{
+		format: options.Format,
 		buffer: ring.New(1024),
 		subs:   make(map[string]*osStream),
 	}