Update: using db transaction

@@ -4,7 +4,11 @@ go 1.14
 
 require (
 	classroom/functions v0.0.0
+	classroom/models v0.0.0
 	github.com/julienschmidt/httprouter v1.3.0
 )
 
-replace classroom/functions v0.0.0 => ../functions
+replace (
+	classroom/functions v0.0.0 => ../functions
+	classroom/models v0.0.0 => ../models
+)

@@ -83,9 +83,17 @@ func (e *Endpoints) ReservationPost(w http.ResponseWriter, r *http.Request, ps h
 		return
 	}
 
+	// Querying with Transaction
+	tx, err := e.DB.Begin()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+	defer tx.Rollback()
+
 	// Querying (Cell Validation Check)
 	isPossible := true
-	rows, err := e.DB.Query(`
+	rows, err := tx.Query(`
 		SELECT cell_start, cell_end
 		FROM transactions
 		WHERE transaction_type=1
@@ -120,8 +128,8 @@ loopCheckingValidation:
 	// Result Resp
 	resp := models.ReservationPostResponse{}
 
-	// Querying (Making a Transaction)
-	res, err := e.DB.Exec(`
+	// Querying
+	res, err := tx.Exec(`
 		INSERT INTO transactions (transaction_type, user_id, timetable_id, lecture, capacity, cell_column, cell_start, cell_end, professor)
 		VALUES (1, (
 			SELECT id FROM users WHERE email=?
@@ -132,6 +140,12 @@ loopCheckingValidation:
 		return
 	}
 
+	err = tx.Commit()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+
 	resp.TransactionID, err = res.LastInsertId()
 	if err != nil {
 		functions.ResponseError(w, 500, err.Error())
@@ -193,16 +207,24 @@ func (e *Endpoints) ReservationDelete(w http.ResponseWriter, r *http.Request, ps
 		}
 	}
 
+	// Querying with Transaction
+	tx, err := e.DB.Begin()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+	defer tx.Rollback()
+
 	// Check Transaction Permission
 	var _transactionType int64
 	var _email string
-	row = e.DB.QueryRow(`
+	row = tx.QueryRow(`
 		SELECT u.email, t.transaction_type
 		FROM transactions AS t, users AS u
 		WHERE t.user_id=u.id
 			AND t.transaction_id=?;
 	`, reservationID)
-	err := row.Scan(&_email, &_transactionType)
+	err = row.Scan(&_email, &_transactionType)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			functions.ResponseError(w, 404, "존재하지 않는 예약")
@@ -221,7 +243,7 @@ func (e *Endpoints) ReservationDelete(w http.ResponseWriter, r *http.Request, ps
 	}
 
 	// Querying
-	res, err := e.DB.Exec(`
+	res, err := tx.Exec(`
 		UPDATE transactions SET transaction_type=0 WHERE transaction_id=?
 	`, reservationID)
 	if err != nil {
@@ -233,5 +255,11 @@ func (e *Endpoints) ReservationDelete(w http.ResponseWriter, r *http.Request, ps
 		return
 	}
 
+	err = tx.Commit()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+
 	functions.ResponseOK(w, "success", nil)
 }

@@ -68,8 +68,27 @@ func (e *Endpoints) UsersPost(w http.ResponseWriter, r *http.Request, ps httprou
 		isSuper = *(reqData.IsSuper)
 	}
 
-	// Querying
-	result, err := e.DB.Exec(`
+	// Querying with Transaction
+	tx, err := e.DB.Begin()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+	defer tx.Rollback()
+
+	row = tx.QueryRow(`
+		SELECT count(id)
+		FROM users
+		WHERE email=?;
+	`, *(reqData.Email))
+	if err = row.Scan(&_count); err == nil {
+		if _count > 0 {
+			functions.ResponseError(w, 500, "이미 존재하는 이메일입니다.")
+			return
+		}
+	}
+
+	result, err := tx.Exec(`
 		INSERT INTO users (email, is_super)
 		VALUES (?, ?);
 	`, *(reqData.Email), isSuper)
@@ -78,6 +97,12 @@ func (e *Endpoints) UsersPost(w http.ResponseWriter, r *http.Request, ps httprou
 		return
 	}
 
+	err = tx.Commit()
+	if err != nil {
+		functions.ResponseError(w, 500, "예기치 못한 에러 : "+err.Error())
+		return
+	}
+
 	// Result
 	resp := models.UsersPostResponse{}
 	resp.UserID, err = result.LastInsertId()