fix golint issues in core/conf (#476)

core/conf/config.go

@@ -16,6 +16,7 @@ var loaders = map[string]func([]byte, interface{}) error{
 	".yml":  LoadConfigFromYamlBytes,
 }
 
+// LoadConfig loads config into v from file, .json, .yaml and .yml are acceptable.
 func LoadConfig(file string, v interface{}, opts ...Option) error {
 	content, err := ioutil.ReadFile(file)
 	if err != nil {
@@ -39,14 +40,17 @@ func LoadConfig(file string, v interface{}, opts ...Option) error {
 	return loader(content, v)
 }
 
+// LoadConfigFromJsonBytes loads config into v from content json bytes.
 func LoadConfigFromJsonBytes(content []byte, v interface{}) error {
 	return mapping.UnmarshalJsonBytes(content, v)
 }
 
+// LoadConfigFromYamlBytes loads config into v from content yaml bytes.
 func LoadConfigFromYamlBytes(content []byte, v interface{}) error {
 	return mapping.UnmarshalYamlBytes(content, v)
 }
 
+// MustLoad loads config into v from path, exits on error.
 func MustLoad(path string, v interface{}, opts ...Option) {
 	if err := LoadConfig(path, v, opts...); err != nil {
 		log.Fatalf("error: config file %s, %s", path, err.Error())

core/conf/options.go

@@ -1,6 +1,7 @@
 package conf
 
 type (
+	// Option defines the method to customize the config options.
 	Option func(opt *options)
 
 	options struct {
@@ -8,6 +9,7 @@ type (
 	}
 )
 
+// UseEnv customizes the config to use environment variables.
 func UseEnv() Option {
 	return func(opt *options) {
 		opt.env = true