swag

Automatically generate RESTful API documentation with Swagger 2.0 for Go.

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Content

• Getting started
• Go web frameworks
• Supported Web Frameworks
• How to use it with Gin
• Implementation Status
• swag cli
• General API Info
• Security
• API Operation
• TIPS
  • User defined structure with an array type
  • Use multiple path params
  • Example value of struct
  • Description of struct
• About the Project

Summary

Swag converts Go annotations to Swagger Documentation 2.0. We've created a variety of plugins for popular Go web frameworks. This allows you to quickly integrate with an existing Go project (using Swagger UI).

Examples

swaggo + gin

Getting started

1. Add comments to your API source code, See Declarative Comments Format.

2. Download swag by using:

$ go get -u github.com/swaggo/swag/cmd/swag

3. Run swag init in the project's root folder which contains the main.go file. This will parse your comments and generate the required files (docs folder and docs/docs.go).

$ swag init

4. In order to serve these files, you can utilize one of our supported plugins. For go's core library, check out net/http.

• Make sure to import the generated docs/docs.go so that your specific configuration gets init'ed.
• If your General API annotation do not live in main.go, you can let swag know with -g.

swag init -g http/api.go

Supported Web Frameworks

• gin
• echo
• buffalo
• net/http

How to use it with Gin

Find the example source code here.

1. After using swag init to generate Swagger 2.0 docs, import the following packages:

import "github.com/swaggo/gin-swagger" // gin-swagger middleware
import "github.com/swaggo/gin-swagger/swaggerFiles" // swagger embed files

2. Add General API annotations in main.go code:

// @title Swagger Example API
// @version 1.0
// @description This is a sample server celler server.
// @termsOfService http://swagger.io/terms/

// @contact.name API Support
// @contact.url http://www.swagger.io/support
// @contact.email [email protected]

// @license.name Apache 2.0
// @license.url http://www.apache.org/licenses/LICENSE-2.0.html

// @host localhost:8080
// @BasePath /api/v1

// @securityDefinitions.basic BasicAuth

// @securityDefinitions.apikey ApiKeyAuth
// @in header
// @name Authorization

// @securitydefinitions.oauth2.application OAuth2Application
// @tokenUrl https://example.com/oauth/token
// @scope.write Grants write access
// @scope.admin Grants read and write access to administrative information

// @securitydefinitions.oauth2.implicit OAuth2Implicit
// @authorizationurl https://example.com/oauth/authorize
// @scope.write Grants write access
// @scope.admin Grants read and write access to administrative information

// @securitydefinitions.oauth2.password OAuth2Password
// @tokenUrl https://example.com/oauth/token
// @scope.read Grants read access
// @scope.write Grants write access
// @scope.admin Grants read and write access to administrative information

// @securitydefinitions.oauth2.accessCode OAuth2AccessCode
// @tokenUrl https://example.com/oauth/token
// @authorizationurl https://example.com/oauth/authorize
// @scope.admin Grants read and write access to administrative information

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

	c := controller.NewController()

	v1 := r.Group("/api/v1")
	{
		accounts := v1.Group("/accounts")
		{
			accounts.GET(":id", c.ShowAccount)
			accounts.GET("", c.ListAccounts)
			accounts.POST("", c.AddAccount)
			accounts.DELETE(":id", c.DeleteAccount)
			accounts.PATCH(":id", c.UpdateAccount)
			accounts.POST(":id/images", c.UploadAccountImage)
		}
    //...
	}
	r.GET("/swagger/*any", ginSwagger.WrapHandler(swaggerFiles.Handler))
	r.Run(":8080")
}
//...

Additionally some general API info can be set dynamically. The generated code package docs exports SwaggerInfo variable which we can use to set the title, description, version, host and base path programatically. Example using Gin:

package main

import (
	"github.com/gin-gonic/gin"
	"github.com/swaggo/gin-swagger"
	"github.com/swaggo/gin-swagger/swaggerFiles"

	"./docs" // docs is generated by Swag CLI, you have to import it.
)

// @contact.name API Support
// @contact.url http://www.swagger.io/support
// @contact.email [email protected]

// @license.name Apache 2.0
// @license.url http://www.apache.org/licenses/LICENSE-2.0.html

// @termsOfService http://swagger.io/terms/

func main() {

	// programatically set swagger info
	docs.SwaggerInfo.Title = "Swagger Example API"
	docs.SwaggerInfo.Description = "This is a sample server Petstore server."
	docs.SwaggerInfo.Version = "1.0"
	docs.SwaggerInfo.Host = "petstore.swagger.io"
	docs.SwaggerInfo.BasePath = "/v2"

	r := gin.New()

	// use ginSwagger middleware to serve the API docs
	r.GET("/swagger/*any", ginSwagger.WrapHandler(swaggerFiles.Handler))

	r.Run()
}

3. Add API Operation annotations in controller code

package controller

import (
	"fmt"
	"net/http"
	"strconv"

	"github.com/gin-gonic/gin"
	"github.com/swaggo/swag/example/celler/httputil"
	"github.com/swaggo/swag/example/celler/model"
)

// ShowAccount godoc
// @Summary Show a account
// @Description get string by ID
// @ID get-string-by-int
// @Accept  json
// @Produce  json
// @Param id path int true "Account ID"
// @Success 200 {object} model.Account
// @Failure 400 {object} httputil.HTTPError
// @Failure 404 {object} httputil.HTTPError
// @Failure 500 {object} httputil.HTTPError
// @Router /accounts/{id} [get]
func (c *Controller) ShowAccount(ctx *gin.Context) {
	id := ctx.Param("id")
	aid, err := strconv.Atoi(id)
	if err != nil {
		httputil.NewError(ctx, http.StatusBadRequest, err)
		return
	}
	account, err := model.AccountOne(aid)
	if err != nil {
		httputil.NewError(ctx, http.StatusNotFound, err)
		return
	}
	ctx.JSON(http.StatusOK, account)
}

// ListAccounts godoc
// @Summary List accounts
// @Description get accounts
// @Accept  json
// @Produce  json
// @Param q query string false "name search by q"
// @Success 200 {array} model.Account
// @Failure 400 {object} httputil.HTTPError
// @Failure 404 {object} httputil.HTTPError
// @Failure 500 {object} httputil.HTTPError
// @Router /accounts [get]
func (c *Controller) ListAccounts(ctx *gin.Context) {
	q := ctx.Request.URL.Query().Get("q")
	accounts, err := model.AccountsAll(q)
	if err != nil {
		httputil.NewError(ctx, http.StatusNotFound, err)
		return
	}
	ctx.JSON(http.StatusOK, accounts)
}

//...

$ swag init

4.Run your app, and browse to http://localhost:8080/swagger/index.html. You will see Swagger 2.0 Api documents as shown below:

Implementation Status

Swagger 2.0 document

• Basic Structure
• API Host and Base Path
• Paths and Operations
• Describing Parameters
• Describing Request Body
• Describing Responses
• MIME Types
• Authentication
  • Basic Authentication
  • API Keys
• Adding Examples
• File Upload
• Enums
• Grouping Operations With Tags
• Swagger Extensions

swag cli

$ swag init -h
NAME:
   swag init - Create docs.go

USAGE:
   swag init [command options] [arguments...]

OPTIONS:
   --generalInfo value, -g value       Go file path in which 'swagger general API Info' is written (default: "main.go")
   --dir value, -d value               Directory you want to parse (default: "./")
   --swagger value, -s value           Output the swagger conf for json and yaml (default: "./docs/swagger")
   --propertyStrategy value, -p value  Property Naming Strategy like snakecase,camelcase,pascalcase (default: "camelcase")

General API Info

Example celler/main.go

annotation	description	example
title	Required. The title of the application.	// @title Swagger Example API
version	Required. Provides the version of the application API.	// @version 1.0
description	A short description of the application.	// @description This is a sample server celler server.
tag.name	Name of a tag.	// @tag.name This is the name of the tag
tag.description	Description of the tag	// @tag.description Cool Description
tag.docs.url	Url of the external Documentation of the tag	// @tag.docs.url https://example.com
tag.docs.descripiton	Description of the external Documentation of the tag	// @tag.docs.descirption Best example documentation
termsOfService	The Terms of Service for the API.	// @termsOfService http://swagger.io/terms/
contact.name	The contact information for the exposed API.	// @contact.name API Support
contact.url	The URL pointing to the contact information. MUST be in the format of a URL.	// @contact.url http://www.swagger.io/support
contact.email	The email address of the contact person/organization. MUST be in the format of an email address.	// @contact.email [email protected]
license.name	Required. The license name used for the API.	// @license.name Apache 2.0
license.url	A URL to the license used for the API. MUST be in the format of a URL.	// @license.url http://www.apache.org/licenses/LICENSE-2.0.html
host	The host (name or ip) serving the API.	// @host localhost:8080
BasePath	The base path on which the API is served.	// @BasePath /api/v1

Security

annotation	description	parameters	example
securitydefinitions.basic	Basic auth.		// @securityDefinitions.basic BasicAuth
securitydefinitions.apikey	API key auth.	in, name	// @securityDefinitions.apikey ApiKeyAuth
securitydefinitions.oauth2.application	OAuth2 application auth.	tokenUrl, scope	// @securitydefinitions.oauth2.application OAuth2Application
securitydefinitions.oauth2.implicit	OAuth2 implicit auth.	authorizationUrl, scope	// @securitydefinitions.oauth2.implicit OAuth2Implicit
securitydefinitions.oauth2.password	OAuth2 password auth.	tokenUrl, scope	// @securitydefinitions.oauth2.password OAuth2Password
securitydefinitions.oauth2.accessCode	OAuth2 access code auth.	tokenUrl, authorizationUrl, scope	// @securitydefinitions.oauth2.accessCode OAuth2AccessCode

parameters annotation	example
in	// @in header
name	// @name Authorization
tokenUrl	// @tokenUrl https://example.com/oauth/token
authorizationurl	// @authorizationurl https://example.com/oauth/authorize
scope.hoge	// @scope.write Grants write access

API Operation

Example celler/controller

annotation	description
description	A verbose explanation of the operation behavior.
id	A unique string used to identify the operation. Must be unique among all API operations.
tags	A list of tags to each API operation that separated by commas.
summary	A short summary of what the operation does.
accept	A list of MIME types the APIs can consume. Value MUST be as described under Mime Types.
produce	A list of MIME types the APIs can produce. Value MUST be as described under Mime Types.
param	Parameters that separated by spaces. param name,param type,data type,is mandatory?,comment attribute(optional)
security	Security to each API operation.
success	Success response that separated by spaces. return code,{param type},data type,comment
failure	Failure response that separated by spaces. return code,{param type},data type,comment
router	Path definition that separated by spaces. path,[httpMethod]

Mime Types

Mime Type	annotation
application/json	application/json, json
text/xml	text/xml, xml
text/plain	text/plain, plain
html	text/html, html
multipart/form-data	multipart/form-data, mpfd
application/x-www-form-urlencoded	application/x-www-form-urlencoded, x-www-form-urlencoded
application/vnd.api+json	application/vnd.api+json, json-api
application/x-json-stream	application/x-json-stream, json-stream
application/octet-stream	application/octet-stream, octet-stream
image/png	image/png, png
image/jpeg	image/jpeg, jpeg
image/gif	image/gif, gif

Security

General API info.

// @securityDefinitions.basic BasicAuth

// @securitydefinitions.oauth2.application OAuth2Application
// @tokenUrl https://example.com/oauth/token
// @scope.write Grants write access
// @scope.admin Grants read and write access to administrative information

Each API operation.

// @Security ApiKeyAuth

Make it AND condition

// @Security ApiKeyAuth
// @Security OAuth2Application[write, admin]

Param Type

• object (struct)
• string (string)
• integer (int, uint, uint32, uint64)
• number (float32)
• boolean (bool)
• array

Data Type

• string (string)
• integer (int, uint, uint32, uint64)
• number (float32)
• boolean (bool)
• user defined struct

Attribute

// @Param enumstring query string false "string enums" Enums(A, B, C)
// @Param enumint query int false "int enums" Enums(1, 2, 3)
// @Param enumnumber query number false "int enums" Enums(1.1, 1.2, 1.3)
// @Param string query string false "string valid" minlength(5) maxlength(10)
// @Param int query int false "int valid" mininum(1) maxinum(10)
// @Param default query string false "string default" default(A)

It also works for the struct fields:

type Foo struct {
    Bar string `minLength:"4" maxLength:"16"`
    Baz int `minimum:"10" maximum:"20" default:"15"`
    Qux []string `enums:"foo,bar,baz"`
}

Available

Field Name	Type	Description
default	*	Declares the value of the parameter that the server will use if none is provided, for example a "count" to control the number of results per page might default to 100 if not supplied by the client in the request. (Note: "default" has no meaning for required parameters.) See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-6.2. Unlike JSON Schema this value MUST conform to the defined type for this parameter.
maximum	number	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.1.2.
minimum	number	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.1.3.
maxLength	integer	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.2.1.
minLength	integer	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.2.2.
enums	[*]	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.5.1.
format	string	The extending format for the previously mentioned type. See Data Type Formats for further details.

Future

Field Name	Type	Description
multipleOf	number	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.1.1.
pattern	string	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.2.3.
maxItems	integer	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.3.2.
minItems	integer	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.3.3.
uniqueItems	boolean	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.3.4.
collectionFormat	string	Determines the format of the array if type array is used. Possible values are: csv - comma separated values foo,bar. ssv - space separated values foo bar. tsv - tab separated values foo\tbar. pipes - pipe separated values foo|bar. multi - corresponds to multiple parameter instances instead of multiple values for a single instance foo=bar&foo=baz. This is valid only for parameters in "query" or "formData". Default value is csv.

TIPS

Descriptions over multiple lines

You can add descriptions spanning multiple lines in either the general api description or routes definitions like so:

// @description This is the first line
// @description This is the second line
// @description And so forth.

User defined structure with an array type

// @Success 200 {array} model.Account <-- This is a user defined struct.

package model

type Account struct {
    ID   int    `json:"id" example:"1"`
    Name string `json:"name" example:"account name"`
}

Use multiple path params

/// ...
// @Param group_id path int true "Group ID"
// @Param account_id path int true "Account ID"
// ...
// @Router /examples/groups/{group_id}/accounts/{account_id} [get]

Example value of struct

type Account struct {
    ID   int    `json:"id" example:"1"`
    Name string `json:"name" example:"account name"`
    PhotoUrls []string `json:"photo_urls" example:"http://test/image/1.jpg,http://test/image/2.jpg"`
}

Description of struct

type Account struct {
    // ID this is userid
    ID   int    `json:"id"
}

Override swagger type of a struct field

type Account struct {
    // Override primitive type by simply specifying it via `swaggertype` tag
    ID     sql.NullInt64 `json:"id" swaggertype:"integer"`

    // Array types can be overridden using "array,<prim_type>" format
    Coeffs []big.Float `json:"coeffs" swaggertype:"array,number"`
}

About the Project

This project was inspired by yvasiyarov/swagger but we simplified the usage and added support a variety of web frameworks.