Update README.md

README.md

@@ -1,5 +1,5 @@
 ## Introduction
-**config** is a simple golang library and designed to read configurations from JSON, Yaml files, environment variables and command line. **config** depends on [go-yaml](https://github.com/go-yaml/yaml) to anlayze Yaml file and use built-in golang library to handle JSON file.
+**config** is a simple golang library and designed to read configurations from JSON, Yaml files, environment variables and command line. **config** depends on [go-yaml](https://github.com/go-yaml/yaml) to anlayze Yaml file and uses built-in golang library to handle JSON file.
 
 ## Installation
 1. Install [Yaml](https://github.com/go-yaml/yaml) library first:
@@ -13,17 +13,35 @@ go get github.com/eschao/config
 ```
 
 ## Usage
-#### Defines **default** values
+#### 1. Defines **default** values
 **config** library supports defining a default value for structure members by using **default** keyword in structure tags
 ```golang
-  type Database struct {
-    Username string `default:"admin"`
-    Password string `default:"admin"`
+  type Log struct {
+    Path  string `default:"/var/logs"`
+    Level string `default:"debug"`
   }
 ```
 
-After specified default value in tags, calls ```config.ParseDefault(interface{})``` to set it on structure instance, example codes as the below:
+After that, calls ```config.ParseDefault(interface{})``` to set it on structure instance, example codes as the below:
+```golang
+  logConfig := Log{}
+  config.ParseDefault(&logConfig)
+```
+
+#### 2. Reads configurations from JSON file
+Like analyzing JSON object from file, reading configurations from JSON file is also simple:
+```golang
+  type Database struct {
+    Host string     `json:"host"`
+    Port int        `json:"port"`
+    Username string `json:"username" default:"admin"`
+    Password string `json:"password" default:"admin"`
+    Log Log         `json:"log"`
+  }
+```
+
+Parsing configurations from JSON:
 ```golang
   dbConfig := Database{}
-  config.ParseDefault(&dbConfig)
+  config.ParseConfigFile(&dbConfig, "config.json")
 ```