feat(login):基本完成用户登录，待测。

repository/abstract.go

@@ -0,0 +1,23 @@
+package repository
+
+func _postProcessSingle[T interface{}](instance *T, has bool, err error) (*T, error) {
+	if err != nil {
+		return nil, err
+	}
+	if has {
+		return instance, nil
+	} else {
+		return nil, nil
+	}
+}
+
+func _postProcessList[T interface{}](instance []*T, has bool, err error) ([]*T, error) {
+	if err != nil {
+		return nil, err
+	}
+	if has {
+		return instance, nil
+	} else {
+		return nil, nil
+	}
+}

repository/user.go

@@ -0,0 +1,22 @@
+package repository
+
+import (
+	"electricity_bill_calc/global"
+	"electricity_bill_calc/model"
+)
+
+type _UserRepository struct{}
+
+var UserRepo _UserRepository
+
+func (_UserRepository) FindUserByUsername(username string) (*model.User, error) {
+	user := new(model.User)
+	has, err := global.DBConn.Where("username=?", username).Get(user)
+	return _postProcessSingle(user, has, err)
+}
+
+func (_UserRepository) RetreiveUserDetail(uid string) (*model.UserDetail, error) {
+	user := new(model.UserDetail)
+	has, err := global.DBConn.Where("id=?", uid).Get(user)
+	return _postProcessSingle(user, has, err)
+}