add json provider

provider/json/provider_example_test.go

@@ -0,0 +1,55 @@
+package json_test
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"gitoa.ru/go-4devs/config"
+	"gitoa.ru/go-4devs/config/provider/json"
+	"gitoa.ru/go-4devs/config/test"
+)
+
+func ExampleClient_Value() {
+	ctx := context.Background()
+
+	// read json config
+	jsonConfig, jerr := fixture.ReadFile("fixture/config.json")
+	if jerr != nil {
+		log.Printf("failed load file:%v", jerr)
+
+		return
+	}
+
+	config, err := config.New(
+		json.New(jsonConfig),
+	)
+	if err != nil {
+		log.Print(err)
+
+		return
+	}
+
+	title, err := config.Value(ctx, "app.name.title")
+	if err != nil {
+		log.Print("app.name.title", err)
+
+		return
+	}
+
+	cfgValue, err := config.Value(ctx, "cfg")
+	if err != nil {
+		log.Print("cfg ", err)
+
+		return
+	}
+
+	cfg := test.Config{}
+	_ = cfgValue.Unmarshal(&cfg)
+
+	fmt.Printf("title from json: %v\n", title.String())
+	fmt.Printf("struct from json: %+v\n", cfg)
+	// Output:
+	// title from json: config title
+	// struct from json: {Duration:21m0s Enabled:true}
+}