diff --git a/doc.go b/doc.go
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+/*
+Package log is a simple and configurable Logging in Go, with level, formatters and writers.
+
+It is completely API compatible with the standard library logger.
+
+The simplest way to use log is simply the package-level exported logger:
+
+package main
+
+    import (
+    	"os"
+    	"github.com/subchen/go-log"
+    )
+
+    func main() {
+    	log.Print("some message")
+    	log.Infof("$HOME = %v", os.Getenv("HOME"))
+    	log.Errorln("Got err:", os.ErrPermission)
+    }
+
+Output:
+
+    07:34:23.039 INFO some message
+    07:34:23.039 INFO $HOME = /home/subchen
+    07:34:23.039 ERROR Got err: permission denied
+
+
+You also can config `log.Default` or new `log.Logger` to customize formatter and writer.
+
+    package main
+
+    import (
+    	"os"
+    	"github.com/subchen/go-log"
+    	"github.com/subchen/go-log/formatters"
+    	"github.com/subchen/go-log/writers"
+    )
+
+    func main() {
+    	logger := &log.Logger{
+    		Level:     log.INFO,
+    		Formatter: new(formatters.TextFormatter),
+    		Out:       &writers.FixedSizeFileWriter{
+    			Name:     "/tmp/test.log",
+    			MaxSize:  10 * 1024 * 1024, // 10m
+    			MaxCount: 10,
+    		},
+    	}
+
+    	logger.Info("some message")
+    }
+
+
+
+Output log in `/tmp/test.log`:
+
+    2018-05-19T07:49:05.979+0000 INFO devbox main 9981 example/main.go:17 some message
+
+
+For a full guide visit https://github.com/subchen/go-log
+
+*/
+package log