use different color library, wrap logger functions with it

logger.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"io"
+	"log"
+
+	c "github.com/fatih/color"
+)
+
+type Logger interface {
+	Printf(format string, v ...interface{})
+	Print(v ...interface{})
+	Println(v ...interface{})
+	Fatal(v ...interface{})
+	Fatalf(format string, v ...interface{})
+}
+
+type logger struct {
+	logger  *log.Logger
+	printer *c.Color
+}
+
+func NewLogger(out io.Writer, prefix string, flag int, color c.Attribute) (l logger) {
+	l.logger = log.New(out, prefix, flag)
+	l.printer = c.New(color)
+	return l
+}
+
+func (l logger) Printf(format string, v ...interface{}) {
+	l.logger.Print(l.printer.Sprintf(format, v...))
+}
+func (l logger) Print(v ...interface{})   { l.logger.Print(l.printer.Sprint(v...)) }
+func (l logger) Println(v ...interface{}) { l.logger.Print(l.printer.Sprintln(v...)) }
+func (l logger) Fatal(v ...interface{})   { l.logger.Fatal(l.printer.Sprint(v...)) }
+func (l logger) Fatalf(format string, v ...interface{}) {
+	l.logger.Fatal(l.printer.Sprintf(format, v...))
+}
+
+type emptyLogger bool
+
+func (l emptyLogger) Printf(format string, v ...interface{}) {}
+func (l emptyLogger) Print(v ...interface{})                 {}
+func (l emptyLogger) Println(v ...interface{})               {}
+func (l emptyLogger) Fatal(v ...interface{})                 {}
+func (l emptyLogger) Fatalf(format string, v ...interface{}) {}