fix golint issues in rest (#529)

rest/config.go

@@ -7,22 +7,25 @@ import (
 )
 
 type (
+	// A PrivateKeyConf is a private key config.
 	PrivateKeyConf struct {
 		Fingerprint string
 		KeyFile     string
 	}
 
+	// A SignatureConf is a signature config.
 	SignatureConf struct {
 		Strict      bool          `json:",default=false"`
 		Expiry      time.Duration `json:",default=1h"`
 		PrivateKeys []PrivateKeyConf
 	}
 
+	// A RestConf is a http service config.
 	// Why not name it as Conf, because we need to consider usage like:
-	// type Config struct {
+	//  type Config struct {
 	//     zrpc.RpcConf
 	//     rest.RestConf
-	// }
+	//  }
 	// if with the name Conf, there will be two Conf inside Config.
 	RestConf struct {
 		service.ServiceConf