implement reference grpc server

pkg/config/custom.go

@@ -8,8 +8,8 @@ import (
 )
 
 type DemoConfig struct {
-	DemoField int       `yaml:"demoField" json:"demoField,omitempty"`
-	DemoType  *DemoOpts `yaml:"demoType" json:"demoType,omitempty"`
+	Timezone string    `yaml:"timezone" json:"timezone,omitempty" default:"UTC"`
+	Opts     *DemoOpts `yaml:"opts" json:"opts,omitempty"`
 
 	// Embeds go-app config, used by go-app to
 	// merge custom config into go-app config, and to produce
@@ -18,6 +18,13 @@ type DemoConfig struct {
 }
 
 type DemoOpts struct {
-	OptField int    `yaml:"optField" json:"optField,omitempty"`
-	OptName  string `yaml:"optName" json:"optName,omitempty"`
+	FactLang string   `yaml:"factLang" json:"factLang,omitempty" default:"en"`
+	FactType FactType `yaml:"factType" json:"factType,omitempty" default:"random" enum:"today,random"`
 }
+
+type FactType string
+
+const (
+	TypeToday  FactType = "today"
+	TypeRandom FactType = "random"
+)