swag

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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).

Contents

• Getting started
• Supported Web Frameworks
• How to use it with Gin
• Implementation Status
• Declarative Comments Format
  • General API Info
  • API Operation
  • Security
• Examples
  • Descriptions over multiple lines
  • User defined structure with an array type
  • Model composition in response
  • Add a headers in response
  • Use multiple path params
  • Example value of struct
  • Description of struct
  • Use swaggertype tag to supported custom type
  • Use swaggerignore tag to exclude a field
  • Add extension info to struct field
  • Rename model to display
  • How to using security annotations
  • Add a description for enum items
• About the Project

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

# 1.16 or newer
$ go install github.com/swaggo/swag/cmd/swag@latest

To build from source you need Go (1.13 or newer).

Or download a pre-compiled binary from the release page.

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

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

swag init -g http/api.go

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: "./")
   --exclude value                        Exclude directories and files when searching, comma separated
   --propertyStrategy value, -p value     Property Naming Strategy like snakecase,camelcase,pascalcase (default: "camelcase")
   --output value, -o value               Output directory for all the generated files(swagger.json, swagger.yaml and doc.go) (default: "./docs")
   --parseVendor                          Parse go files in 'vendor' folder, disabled by default (default: false)
   --parseDependency                      Parse go files in outside dependency folder, disabled by default (default: false)
   --markdownFiles value, --md value      Parse folder containing markdown files to use as description, disabled by default
   --codeExampleFiles value, --cef value  Parse folder containing code example files to use for the x-codeSamples extension, disabled by default
   --parseInternal                        Parse go files in internal packages, disabled by default (default: false)
   --generatedTime                        Generate timestamp at the top of docs.go, disabled by default (default: false)
   --parseDepth value                     Dependency parse depth (default: 100)
   --instanceName value                   Set the swagger document instance name (default: "swagger")
   --help, -h                             show help (default: false)

Supported Web Frameworks

• gin
• echo
• buffalo
• net/http
• flamingo
• fiber
• atreugo

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/files" // 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
// @query.collection.format multi

// @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

// @x-extension-openapi {"example": "value on a json format"}

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 programmatically. Example using Gin:

package main

import (
	"github.com/gin-gonic/gin"
	"github.com/swaggo/files"
	"github.com/swaggo/gin-swagger"
	
	"./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() {

	// programmatically 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"
	docs.SwaggerInfo.Schemes = []string{"http", "https"}
		
	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
// @Header 200 {string} Token "qwerty"
// @Failure 400,404 {object} httputil.HTTPError
// @Failure 500 {object} httputil.HTTPError
// @Failure default {object} httputil.DefaultError
// @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
// @Header 200 {string} Token "qwerty"
// @Failure 400,404 {object} httputil.HTTPError
// @Failure 500 {object} httputil.HTTPError
// @Failure default {object} httputil.DefaultError
// @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

Declarative Comments Format

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.description	Description of the external Documentation of the tag	// @tag.docs.description 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
accept	A list of MIME types the APIs can consume. Note that Accept only affects operations with a request body, such as POST, PUT and PATCH. Value MUST be as described under Mime Types.	// @accept json
produce	A list of MIME types the APIs can produce. Value MUST be as described under Mime Types.	// @produce json
query.collection.format	The default collection(array) param format in query,enums:csv,multi,pipes,tsv,ssv. If not set, csv is the default.	// @query.collection.format multi
schemes	The transfer protocol for the operation that separated by spaces.	// @schemes http https
x-name	The extension key, must be start by x- and take only json value	// @x-example-key {"key": "value"}

Using markdown descriptions

When a short string in your documentation is insufficient, or you need images, code examples and things like that you may want to use markdown descriptions. In order to use markdown descriptions use the following annotations.

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.markdown	A short description of the application. Parsed from the api.md file. This is an alternative to @description	// @description.markdown No value needed, this parses the description from api.md
tag.name	Name of a tag.	// @tag.name This is the name of the tag
tag.description.markdown	Description of the tag this is an alternative to tag.description. The description will be read from a file named like tagname.md	// @tag.description.markdown

API Operation

Example celler/controller

annotation	description
description	A verbose explanation of the operation behavior.
description.markdown	A short description of the application. The description will be read from a file named like endpointname.md
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. Note that Accept only affects operations with a request body, such as POST, PUT and PATCH. 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 or default,{param type},data type,comment
failure	Failure response that separated by spaces. return code or default,{param type},data type,comment
response	As same as success and failure
header	Header in response that separated by spaces. return code,{param type},data type,comment
router	Path definition that separated by spaces. path,[httpMethod]
x-name	The extension key, must be start by x- and take only json value.
x-codeSample	Optional Markdown usage. take file as parameter. This will then search for a file named like the summary in the given folder.
deprecated	Mark endpoint as deprecated.

Mime Types

swag accepts all MIME Types which are in the correct format, that is, match */*. Besides that, swag also accepts aliases for some MIME Types as follows:

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

Param Type

• query
• path
• header
• body
• formData

Data Type

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

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

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" minimum(1) maximum(10)
// @Param default query string false "string default" default(A)
// @Param collection query []string false "string collection" collectionFormat(multi)
// @Param extensions query []string false "string collection" extensions(x-example=test,x-nullable)

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
validate	string	Determines the validation for the parameter. Possible values are: required.
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.
multipleOf	number	See https://tools.ietf.org/html/draft-fge-json-schema-validation-00#section-5.1.1.
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.
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.
extensions	string	Add extension to parameters.

Future

Field Name	Type	Description
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.

Examples

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"`
}

Model composition in response

// JSONResult's data field will be overridden by the specific type proto.Order
@success 200 {object} jsonresult.JSONResult{data=proto.Order} "desc"

type JSONResult struct {
    Code    int          `json:"code" `
    Message string       `json:"message"`
    Data    interface{}  `json:"data"`
}

type Order struct { //in `proto` package
    Id  uint            `json:"id"`
    Data  interface{}   `json:"data"`
}

• also support array of objects and primitive types as nested response

@success 200 {object} jsonresult.JSONResult{data=[]proto.Order} "desc"
@success 200 {object} jsonresult.JSONResult{data=string} "desc"
@success 200 {object} jsonresult.JSONResult{data=[]string} "desc"

• overriding multiple fields. field will be added if not exists

@success 200 {object} jsonresult.JSONResult{data1=string,data2=[]string,data3=proto.Order,data4=[]proto.Order} "desc"

• overriding deep-level fields

type DeepObject struct { //in `proto` package
	...
}
@success 200 {object} jsonresult.JSONResult{data1=proto.Order{data=proto.DeepObject},data2=[]proto.Order{data=[]proto.DeepObject}} "desc"

Add a headers in response

// @Success 200 {string} string	"ok"
// @failure 400 {string} string	"error"
// @response default {string} string	"other error"
// @Header 200 {string} Location "/entity/1"
// @Header 200,400,default {string} Token "token"
// @Header all {string} Token2 "token2"

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]

Add multiple paths

/// ...
// @Param group_id path int true "Group ID"
// @Param user_id path int true "User ID"
// ...
// @Router /examples/groups/{group_id}/user/{user_id}/address [put]
// @Router /examples/user/{user_id}/address [put]

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"`
	Name string `json:"name"` // This is Name
}

Use swaggertype tag to supported custom type

#201

type TimestampTime struct {
    time.Time
}

///implement encoding.JSON.Marshaler interface
func (t *TimestampTime) MarshalJSON() ([]byte, error) {
    bin := make([]byte, 16)
    bin = strconv.AppendInt(bin[:0], t.Time.Unix(), 10)
    return bin, nil
}

func (t *TimestampTime) UnmarshalJSON(bin []byte) error {
    v, err := strconv.ParseInt(string(bin), 10, 64)
    if err != nil {
        return err
    }
    t.Time = time.Unix(v, 0)
    return nil
}
///

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

    // Override struct type to a primitive type 'integer' by specifying it via `swaggertype` tag
    RegisterTime TimestampTime `json:"register_time" swaggertype:"primitive,integer"`

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

#379

type CerticateKeyPair struct {
	Crt []byte `json:"crt" swaggertype:"string" format:"base64" example:"U3dhZ2dlciByb2Nrcw=="`
	Key []byte `json:"key" swaggertype:"string" format:"base64" example:"U3dhZ2dlciByb2Nrcw=="`
}

generated swagger doc as follows:

"api.MyBinding": {
  "type":"object",
  "properties":{
    "crt":{
      "type":"string",
      "format":"base64",
      "example":"U3dhZ2dlciByb2Nrcw=="
    },
    "key":{
      "type":"string",
      "format":"base64",
      "example":"U3dhZ2dlciByb2Nrcw=="
    }
  }
}

Use swaggerignore tag to exclude a field

type Account struct {
    ID   string    `json:"id"`
    Name string     `json:"name"`
    Ignored int     `swaggerignore:"true"`
}

Add extension info to struct field

type Account struct {
    ID   string    `json:"id"   extensions:"x-nullable,x-abc=def,!x-omitempty"` // extensions fields must start with "x-"
}

generate swagger doc as follows:

"Account": {
    "type": "object",
    "properties": {
        "id": {
            "type": "string",
            "x-nullable": true,
            "x-abc": "def",
            "x-omitempty": false
        }
    }
}

Rename model to display

type Resp struct {
	Code int
}//@name Response

How to using security annotations

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]

Add a description for enum items

type Example struct {
	// Sort order:
	// * asc - Ascending, from A to Z.
	// * desc - Descending, from Z to A.
	Order string `enums:"asc,desc"`
}

About the Project

This project was inspired by yvasiyarov/swagger but we simplified the usage and added support a variety of web frameworks. Gopher image source is tenntenn/gopher-stickers. It has licenses creative commons licensing.

Contributors

This project exists thanks to all the people who contribute. [Contribute].

Backers

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License