Getting Started with goa

package design                                     // 当前目录为 design 所以包名也该是 design

import (
        . "github.com/goadesign/goa/design"        // 使用 . 导入保证 DSL 功能启用；以下并没有使用这两个包
        . "github.com/goadesign/goa/design/apidsl"
)

var _ = API("cellar", func() {                     // API 函数定义了微服务的端点以及其他全局属性。在设计中必须只存在一个 API 定义。
        Title("The virtual wine cellar")           
        Description("A simple goa service")        
        Scheme("http")                             
        Host("localhost:8080")
})

var _ = Resource("bottle", func() {                // 使用 Resource 函数定义一个名为 bottle 的资源。
        BasePath("/bottles")                       
        DefaultMedia(BottleMedia)                  

        Action("show", func() {                    // 使用 Action 函数定义一个资源行为，资源行为定义在 Resource 内部。
                Description("Get bottle by id")    
                Routing(GET("/:bottleID"))         
                Params(func() {                    
                        Param("bottleID", Integer, "Bottle ID")
                })
                Response(OK)                       
                Response(NotFound)                 
        })
})

// BottleMedia defines the media type used to render bottles.
var BottleMedia = MediaType("application/vnd.goa.example.bottle+json", func() {
        Description("A bottle of wine")
        Attributes(func() {                         // Attributes define the media type shape.
                Attribute("id", Integer, "Unique bottle ID")
                Attribute("href", String, "API href for making requests on the bottle")
                Attribute("name", String, "Name of wine")
                Required("id", "href", "name")
        })
        View("default", func() {                    // View defines a rendering of the media type.
                Attribute("id")                     // Media types may have multiple views and must
                Attribute("href")                   // have a "default" view.
                Attribute("name")
        })
})

type BottleController interface {
        goa.Muxer
        Show(*ShowBottleContext) error
}

// ShowBottleContext provides the bottle show action context.
type ShowBottleContext struct {
        context.Context
        *goa.ResponseData
        *goa.RequestData
        BottleID int
}

// OK sends a HTTP response with status code 200.
func (ctx *ShowBottleContext) OK(r *GoaExampleBottle) error {
        ctx.ResponseData.Header().Set("Content-Type", "application/vnd.goa.example.bottle")
        return ctx.Service.Send(ctx.Context, 200, r)
}

// NotFound sends a HTTP response with status code 404.
func (ctx *ShowBottleContext) NotFound() error {
        ctx.ResponseData.WriteHeader(404)
        return nil
}

// Show implements the "show" action of the "bottles" controller.
func (c *BottleController) Show(ctx *app.ShowBottleContext) error {
        if ctx.BottleID == 0 {
                // Emulate a missing record with ID 0
                return ctx.NotFound()
        }
        // Build the resource using the generated data structure
        bottle := app.GoaExampleBottle{
                ID:   ctx.BottleID,
                Name: fmt.Sprintf("Bottle #%d", ctx.BottleID),
                Href: app.BottleHref(ctx.BottleID),
        }

        // Let the generated code produce the HTTP response using the
        // media type described in the design (BottleMedia).
        return ctx.OK(&bottle)
}

func main() {
        // Create service
        service := goa.New("cellar")

        // Mount middleware
        service.Use(middleware.RequestID())
        service.Use(middleware.LogRequest(true))
        service.Use(middleware.ErrorHandler(service, true))
        service.Use(middleware.Recover())

        // Mount "bottle" controller
        c := NewBottleController(service)
        app.MountBottleController(service, c)

        // Start service
        if err := service.ListenAndServe(":8080"); err != nil {
                service.LogError("startup", "err", err)
        }
}

go build -o cellar
./cellar