[FEATURE] it's option to set case sensitive

.gitignore

@@ -3,3 +3,5 @@
 /build/
 /var/
 /vendor/
+go.mod
+go.sum

README.md

@@ -139,6 +139,42 @@ if err := viper.ReadInConfig(); err != nil {
 
 *NOTE [since 1.6]:* You can also have a file without an extension and specify the format programmaticaly. For those configuration files that lie in the home of the user without any extension like `.bashrc`
 
+### MapTo
+- source file
+```yaml
+service:
+	port: 1234
+	ip: "127.0.0.1"
+version: 1.0.01
+```
+- use MapTo
+
+```go
+type Service struct {
+	Port int `viper:"port"`
+	IP string `viper:"ip"`
+}
+//your prepare code ...
+
+var service Service
+var version string
+
+if err := viper.MapTo("service",&service); err != nil {
+	//error handler...
+}
+if err := viper.MapTo("version",&version); err != nil {
+	//error handler...
+}
+
+
+
+log.Println(service,version)
+
+//....
+
+```
+
+
 ### Writing Config Files
 
 Reading from config files is useful, but at times you want to store all modifications made at run time.
@@ -862,7 +898,16 @@ application foundation needs.
 Is there a better name for a [commander](http://en.wikipedia.org/wiki/Cobra_Commander)?
 
 ### Does Viper support case sensitive keys?
+#### [FEATURE] surport case sensitive
+```go
+// if you want to keep case insensitive, you can do nothing
+// but if you want to make it case sensitive, please do the following step
+func main(){
+	viper.SetCaseSensitive()
 
+	// your code next...
+}
+```
 **tl;dr:** No.
 
 Viper merges configuration from various sources, many of which are either case insensitive or uses different casing than the rest of the sources (eg. env vars).