📝 Update: Add JSONDecoder to config (#1489)

* 📝 Update: Add JSONDecoder to config

app.go

@@ -308,6 +308,13 @@ type Config struct {
 	// Default: json.Marshal
 	JSONEncoder utils.JSONMarshal `json:"-"`
 
+	// When set by an external client of Fiber it will use the provided implementation of a
+	// JSONUnmarshal
+	//
+	// Allowing for flexibility in using another json library for encoding
+	// Default: json.Unmarshal
+	JSONDecoder utils.JSONUnmarshal `json:"-"`
+
 	// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only)
 	// WARNING: When prefork is set to true, only "tcp4" and "tcp6" can be chose.
 	//
@@ -459,6 +466,9 @@ func New(config ...Config) *App {
 	if app.config.JSONEncoder == nil {
 		app.config.JSONEncoder = json.Marshal
 	}
+	if app.config.JSONDecoder == nil {
+		app.config.JSONDecoder = json.Unmarshal
+	}
 	if app.config.Network == "" {
 		app.config.Network = NetworkTCP4
 	}

ctx.go

@@ -291,7 +291,7 @@ func (c *Ctx) BodyParser(out interface{}) error {
 	// Parse body accordingly
 	if strings.HasPrefix(ctype, MIMEApplicationJSON) {
 		schemaDecoder.SetAliasTag("json")
-		return json.Unmarshal(c.Body(), out)
+		return c.app.config.JSONDecoder(c.Body(), out)
 	}
 	if strings.HasPrefix(ctype, MIMEApplicationForm) {
 		schemaDecoder.SetAliasTag("form")