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
• The swag formatter
• Implementation Status
• Declarative Comments Format
  • General API Info
  • API Operation
  • Security
• Examples
  • Descriptions over multiple lines
  • User defined structure with an array type
  • Function scoped struct declaration
  • Model composition in response
  • Add a headers in response
  • Use multiple path params
  • Example value of struct
  • SchemaExample of body
  • Description of struct
  • Use swaggertype tag to supported custom type
  • Use global overrides to support a custom type
  • Use swaggerignore tag to exclude a field
  • Add extension info to struct field
  • Rename model to display
  • How to use security annotations
  • Add a description for enum items
  • Generate only specific docs file types
  • How to use Go generic types
• About the Project

Getting started

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

2. Install swag by using:

go install github.com/swaggo/swag/cmd/swag@latest

To build from source you need Go (1.19 or newer).

Alternatively you can run the docker image:

docker run --rm -v $(pwd):/code ghcr.io/swaggo/swag:latest

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.

import _ "example-module-name/docs"

swag init -g http/api.go

4. (optional) Use swag fmt format the SWAG comment. (Please upgrade to the latest version)

swag fmt

swag cli

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

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

OPTIONS:
   --quiet, -q                            Make the logger quiet. (default: false)
   --generalInfo value, -g value          Go file path in which 'swagger general API Info' is written (default: "main.go")
   --dir value, -d value                  Directories you want to parse,comma separated and general-info file must be in the first one (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 docs.go) (default: "./docs")
   --outputTypes value, --ot value        Output types of generated files (docs.go, swagger.json, swagger.yaml) like go,json,yaml (default: "go,json,yaml")
   --parseVendor                          Parse go files in 'vendor' folder, disabled by default (default: false)
   --parseDependency, --pd                Parse go files inside 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)
   --requiredByDefault                    Set validation required for all fields by default (default: false)
   --instanceName value                   This parameter can be used to name different swagger document instances. It is optional.
   --overridesFile value                  File to read global type overrides from. (default: ".swaggo")
   --parseGoList                          Parse dependency via 'go list' (default: true)
   --tags value, -t value                 A comma-separated list of tags to filter the APIs for which the documentation is generated.Special case if the tag is prefixed with the '!' character then the APIs with that tag will be excluded
   --templateDelims value, --td value     Provide custom delimiters for Go template generation. The format is leftDelim,rightDelim. For example: "[[,]]"
   --collectionFormat value, --cf value   Set default collection format (default: "csv")
   --state value                          Initial state for the state machine (default: ""), @HostState in root file, @State in other files
   --parseFuncBody                        Parse API info within body of functions in go files, disabled by default (default: false)
   --help, -h                             show help (default: false)

swag fmt -h
NAME:
   swag fmt - format swag comments

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

OPTIONS:
   --dir value, -d value          Directories you want to parse,comma separated and general-info file must be in the first one (default: "./")
   --exclude value                Exclude directories and files when searching, comma separated
   --generalInfo value, -g value  Go file path in which 'swagger general API Info' is written (default: "main.go")
   --help, -h                     show help (default: false)

Supported Web Frameworks

• gin
• echo
• buffalo
• net/http
• gorilla/mux
• go-chi/chi
• flamingo
• fiber
• atreugo
• hertz

How to use it with Gin

Find the example source code here.

Finish the steps in Getting started

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  support@swagger.io

// @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

// @externalDocs.description  OpenAPI
// @externalDocs.url          https://swagger.io/resources/open-api/
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  support@swagger.io

// @license.name  Apache 2.0
// @license.url   http://www.apache.org/licenses/LICENSE-2.0.html
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 an account
// @Description  get string by ID
// @Tags         accounts
// @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
// @Tags         accounts
// @Accept       json
// @Produce      json
// @Param        q    query     string  false  "name search by q"  Format(email)
// @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:

The swag formatter

The Swag Comments can be automatically formatted, just like 'go fmt'. Find the result of formatting here.

Usage:

swag fmt

Exclude folder：

swag fmt -d ./ --exclude ./internal

When using swag fmt, you need to ensure that you have a doc comment for the function to ensure correct formatting. This is due to swag fmt indenting swag comments with tabs, which is only allowed after a standard doc comment.

For example, use

// ListAccounts lists all existing accounts
//
//  @Summary      List accounts
//  @Description  get accounts
//  @Tags         accounts
//  @Accept       json
//  @Produce      json
//  @Param        q    query     string  false  "name search by q"  Format(email)
//  @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) {

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

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.

API Operation

Example celler/controller

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:

Param Type

• query
• path
• header
• body
• formData

Data Type

• string (string)
• integer (int, uint, uint32, uint64)
• number (float32)
• boolean (bool)
• file (param data type when uploading)
• user defined struct

Security

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   example     query     string     false  "string example"     example(string)
// @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" example:"random string"`
    Baz int `minimum:"10" maximum:"20" default:"15"`
    Qux []string `enums:"foo,bar,baz"`
}

Available

Future

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"`
}

Function scoped struct declaration

You can declare your request response structs inside a function body. You must have to follow the naming convention <package-name>.<function-name>.<struct-name> .

package main

// @Param request body main.MyHandler.request true "query params"
// @Success 200 {object} main.MyHandler.response
// @Router /test [post]
func MyHandler() {
	type request struct {
		RequestField string
	}

	type response struct {
		ResponseField string
	}
}

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"`
}

SchemaExample of body

// @Param email body string true "message/rfc822" SchemaExample(Subject: Testmail\r\n\r\nBody Message\r\n)

Description of struct

// Account model info
// @Description User account information
// @Description with user id and username
type Account struct {
	// ID this is userid
	ID   int    `json:"id"`
	Name string `json:"name"` // This is Name
}

#708 The parser handles only struct comments starting with @Description attribute. But it writes all struct field comments as is.

So, generated swagger doc as follows:

"Account": {
  "type":"object",
  "description": "User account information with user id and username"
  "properties": {
    "id": {
      "type": "integer",
      "description": "ID this is userid"
    },
    "name": {
      "type":"string",
      "description": "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 global overrides to support a custom type

If you are using generated files, the swaggertype or swaggerignore tags may not be possible.

By passing a mapping to swag with --overridesFile you can tell swag to use one type in place of another wherever it appears. By default, if a .swaggo file is present in the current directory it will be used.

Go code:

type MyStruct struct {
  ID     sql.NullInt64 `json:"id"`
  Name   sql.NullString `json:"name"`
}

.swaggo:

// Replace all NullInt64 with int
replace database/sql.NullInt64 int

// Don't include any fields of type database/sql.NullString in the swagger docs
skip    database/sql.NullString

Possible directives are comments (beginning with //), replace path/to/a.type path/to/b.type, and skip path/to/a.type.

(Note that the full paths to any named types must be provided to prevent problems when multiple packages define a type with the same name)

Rendered:

"types.MyStruct": {
  "id": "integer"
}

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 use 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]

Make it OR condition

// @Security ApiKeyAuth || firebase
// @Security OAuth2Application[write, admin] || APIKeyAuth

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"`
}

Generate only specific docs file types

By default swag command generates Swagger specification in three different files/file types:

• docs.go
• swagger.json
• swagger.yaml

If you would like to limit a set of file types which should be generated you can use --outputTypes (short -ot) flag. Default value is go,json,yaml - output types separated with comma. To limit output only to go and yaml files, you would write go,yaml. With complete command that would be swag init --outputTypes go,yaml.

How to use Generics

// @Success 200 {object} web.GenericNestedResponse[types.Post]
// @Success 204 {object} web.GenericNestedResponse[types.Post, Types.AnotherOne]
// @Success 201 {object} web.GenericNestedResponse[web.GenericInnerType[types.Post]]
func GetPosts(w http.ResponseWriter, r *http.Request) {
	_ = web.GenericNestedResponse[types.Post]{}
}

See this file for more details and other examples.

Change the default Go Template action delimiters

#980 #1177

If your swagger annotations or struct fields contain "{{" or "}}", the template generation will most likely fail, as these are the default delimiters for go templates.

To make the generation work properly, you can change the default delimiters with -td. For example:

swag init -g http/api.go -td "[[,]]"

The new delimiter is a string with the format "<left delimiter>,<right delimiter>".

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

Thank you to all our backers! 🙏 [Become a backer]

Sponsors

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License