resolve error strings, log error

config.go

@@ -16,14 +16,14 @@ type Value struct {
 func (c Config) Value(key string) Value {
 	foundValue, err := getType(key, c)
 	if err != nil {
-		logError(err)
 		return Value{value: nil, err: err}
 	}
 	return Value{value: foundValue, err: nil}
 }
 
 func (v Value) Bool() (*bool, error) {
 	if err := v.error(reflect.Bool); err != nil {
+		logError(err)
 		return nil, err
 	} else {
 		value := v.value.(bool)
@@ -33,6 +33,7 @@ func (v Value) Bool() (*bool, error) {
 
 func (v Value) Int() (*int, error) {
 	if err := v.error(reflect.Float64); err != nil {
+		logError(err)
 		return nil, err
 	} else {
 		value := int(v.value.(float64))
@@ -42,6 +43,7 @@ func (v Value) Int() (*int, error) {
 
 func (v Value) Float() (*float64, error) {
 	if err := v.error(reflect.Float64); err != nil {
+		logError(err)
 		return nil, err
 	} else {
 		value := v.value.(float64)
@@ -51,6 +53,7 @@ func (v Value) Float() (*float64, error) {
 
 func (v Value) String() (*string, error) {
 	if err := v.error(reflect.String); err != nil {
+		logError(err)
 		return nil, err
 	} else {
 		value := v.value.(string)
@@ -60,8 +63,8 @@ func (v Value) String() (*string, error) {
 
 func (v Value) error(t reflect.Kind) error {
 	kind := reflect.ValueOf(v.value).Kind()
-	if kind != t {
-		return errors.New(fmt.Sprintf("type of value should be %s", kind))
+	if v.err == nil && kind != t {
+		return errors.New(fmt.Sprintf("type of value should be '%s', please use '%s()' function", kind, kind))
 	}
 	return v.err
 }
@@ -80,5 +83,5 @@ func getType(key string, config Config) (interface{}, error) {
 }
 
 func errKeyNotFound(key string) error {
-	return errors.New(fmt.Sprintf("given key %s not exists in configuration", key))
+	return errors.New(fmt.Sprintf("given key '%s' not exists in configuration", key))
 }