Golang の echo で MariaDB の Read

次のページを参考にしました。
Golang+Echo+dbrでMySQLのCRUDをする／JSONでDBの値を返却する話

MariaDB から読んだデータを、JSONで出力します。

Mysql への接続情報

User: scott
Password: tiger123
データベース: city
テーブル名: cities

MariaDB の状態

$ mysql -uscott -ptiger123 city
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 24
Server version: 10.1.33-MariaDB MariaDB Server

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [city]> select * from cities;
+-------+--------+------------+------------+
| id    | name   | population | date_mod   |
+-------+--------+------------+------------+
| t3321 | 岡山   |     725139 | 2002-2-9   |
| t3322 | 倉敷   |     417328 | 2002-5-15  |
| t3323 | 津山   |     891654 | 2002-7-21  |
| t3324 | 玉野   |     265981 | 2002-11-12 |
| t3325 | 笠岡   |     284597 | 2002-4-24  |
| t3326 | 井原   |     671942 | 2002-2-8   |
| t3327 | 総社   |     265481 | 2002-8-3   |
| t3328 | 高梁   |     792356 | 2002-3-14  |
| t3329 | 新見   |     415892 | 2002-1-15  |
+-------+--------+------------+------------+
9 rows in set (0.00 sec)

MariaDB [city]>

server.go

// -----------------------------------------------------------------------
/*
    server.go

                        Jun/11/2018
*/
// -----------------------------------------------------------------------
package main

import (
    "net/http"
    "github.com/labstack/echo"
    "github.com/labstack/echo/middleware"

    _ "github.com/go-sql-driver/mysql"

    "github.com/gocraft/dbr"
)

type (
    cityinfo struct {
    ID   string     `db:"id"`
    Name string  `db:"name"`
    Population int  `db:"population"`
    Date_mod string  `db:"date_mod"`
    }

    responseData struct {
    Users   []cityinfo      `json:"cities"`
    }
)

var (
    tablename = "cities"
    seq   = 1
    conn, _ = dbr.Open("mysql", "scott:tiger123@tcp(127.0.0.1:3306)/city", nil)
    sess = conn.NewSession(nil)
)

// -----------------------------------------------------------------------
func selectCities(c echo.Context) error {
    var u []cityinfo

    sess.Select("*").From(tablename).Load(&u)
    response := new(responseData)
    response.Users = u
    return c.JSON(http.StatusOK,response)
}

// -----------------------------------------------------------------------
func main() {
    e := echo.New()

    // Middleware
    e.Use(middleware.Logger())
    e.Use(middleware.Recover())

    // Routes

    e.GET("/cities/",selectCities)

    // Start server
    e.Start(":1323")
}

// -----------------------------------------------------------------------

サーバーの起動

go run server.go

クライアントでアクセス

curl http://localhost:1323/cities/ | jq .