Go × Echoで始めるWebサーバ構築入門：シンプル・高速なAPI開発を最短で学ぶ

mkdir go-echo-example
cd go-echo-example
go mod init go-echo-example

$ go get github.com/labstack/echo/v4

package main

import (
	"net/http"

	"github.com/labstack/echo/v4"
)

func main() {
	e := echo.New()
	e.GET("/", func(c echo.Context) error {
		return c.String(http.StatusOK, "Hello, Echo!")
	})

	e.Logger.Fatal(e.Start(":8080"))
}

go run main.go

go-echo-example/
├── go.mod
├── main.go
├── handler/       // HTTPハンドラー
├── service/       // ビジネスロジック層
├── repository/    // データアクセス層
└── model/         // ドメインモデル

go install github.com/air-verse/air@latest

# .air.toml
root = "."
tmp_dir = "tmp"

[build]
  cmd = "go build -o ./tmp/main ."
  bin = "tmp/main"
  include_ext = ["go"]
  exclude_dir = ["tmp", "vendor"]

[log]
  time = true

air

package main

import (
	"net/http"

	"github.com/labstack/echo/v4"
)

func main() {
	e := echo.New()
	e.GET("/", func(c echo.Context) error {
		return c.String(http.StatusOK, "Hello, Echo!")
	})

	e.Start(":8080")
}

+ e.GET("/search", func(c echo.Context) error {
+ 	keyword := c.QueryParam("q")
+ 	return c.String(http.StatusOK, "query: "+keyword)
+ })

curl 'http://localhost:8080/search?q=golang'

"query": "golang"

+ e.GET("/users/:id", func(c echo.Context) error {
+ 	id := c.Param("id")
+ 	return c.String(http.StatusOK, "user_id: "+id)
+ })

curl http://localhost:8080/users/123

"user_id": "123"

+ e.POST("/login", func(c echo.Context) error {
+ 	username := c.FormValue("username")
+ 	password := c.FormValue("password")
+ 	return c.String(http.StatusOK, "user_name: "+username+", password: "+password)
+ })

curl -X POST -d "name=Gopher&password=p1234567" http://localhost:8080/login

user_name: , password:p1234567

+ type Message struct {
+ 	Title   string `json:"title"`
+ 	Content string `json:"content"`
+ }

func main() {
	r := gin.Default()

※一部省略

+ e.POST("/messages", func(c echo.Context) error {
+ 	msg := new(Message)
+ 	if err := c.Bind(msg); err != nil {
+ 		return err
+ 	}
+ 	return c.JSON(http.StatusOK, msg)
+ })
}

curl -X POST http://localhost:8080/messages \
  -H "Content-Type: application/json" \
  -d '{"title": "Hello", "content": "This is a test message"}'

{"title":"Hello","content":"This is a test message"}

e.GET("/json", func(c echo.Context) error {
	msg := Message{
		Title:   "Hello",
		Content: "This is a JSON response",
	}
	return c.JSON(http.StatusOK, msg)
})

 curl http://localhost:8080/json

{"title":"Hello","content":"This is a JSON response"}

e.GET("/html", func(c echo.Context) error {
	html := `<h1>Welcome</h1><p>This is HTML content.</p>`
	return c.HTML(http.StatusOK, html)
})

e.GET("/notfound", func(c echo.Context) error {
	return c.String(http.StatusNotFound, "Not Found")
})

curl -i http://localhost:8080/notfound

HTTP/1.1 404 Not Found
Content-Type: text/plain; charset=UTF-8
Date: Mon, 16 Jun 2025 00:31:15 GMT
Content-Length: 9

Not Found

import (
	"net/http"

	"github.com/labstack/echo/v4"
+	"github.com/labstack/echo/v4/middleware"
)

e := echo.New()

+ e.Use(middleware.Logger())
+ e.Use(middleware.Recover())

※一部省略

+	e.GET("/panic", func(c echo.Context) error {
+		panic("something went wrong")
+	})

{"time":"2025-06-16T09:46:37.223514+09:00","id":"","remote_ip":"::1","host":"localhost:8080","method":"GET","uri":"/notfound","user_agent":"curl/8.7.1","status":404,"error":"","latency":9333,"latency_human":"9.333µs","bytes_in":0,"bytes_out":9}

curl http://localhost:8080/panic

{"message":"Internal Server Error"}

func myMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		// 前処理
		println("Before handler")

		// ハンドラー本体の呼び出し
		err := next(c)

		// 後処理
		println("After handler")
		return err
	}
}

e.Use(myMiddleware)

+	g := e.Group("")
+	g.Use(myMiddleware)
-	e.GET("/notfound", func(c echo.Context) error {
+	g.GET("/notfound", func(c echo.Context) error {
		return c.String(http.StatusNotFound, "Not Found")
	})

curl -i http://localhost:8080/notfound