fix: err code 迁移到各自的包下 (#65)

jsonUtil/err_code.go

@@ -0,0 +1,16 @@
+package jsonUtil
+
+import (
+	"errors"
+	"strconv"
+)
+
+var (
+	// ErrSyntax indicates that a value does not have the right syntax for the target type
+	// 指示值不具有目标类型的正确语法
+	ErrSyntax = strconv.ErrSyntax
+
+	// ErrType indicates that a value does not have the right syntax for the target type
+	// 指示值不具有目标类型的正确语法
+	ErrType = errors.New("unsupported type")
+)