A modern, simple, fast & opinionated REST API framework for Go with batteries included. Pronounced IPA: /'hjuːmɑ/. The goals of this project are to provide:

• A modern REST API backend framework for Go developers
  • Described by OpenAPI 3 & JSON Schema
  • First class support for middleware, JSON, and other features
• Guard rails to prevent common mistakes
• Documentation that can't get out of date
• High-quality developer tooling

Features include:

• HTTP, HTTPS (TLS), and HTTP/2 built-in
  • Let's Encrypt auto-updating certificates via --autotls
• Declarative interface on top of Gin
  • Operation & model documentation
  • Request params (path, query, or header)
  • Request body
  • Responses (including errors)
  • Response headers
• Default (optional) middleware
  • Automatic recovery from panics
  • Automatically handle CORS headers
  • Structured logging middleware using Zap
• Annotated Go types for input and output models
  • Generates JSON Schema from Go types
  • Automatic input model validation & error handling
• Dependency injection for loggers, datastores, etc
• Documentation generation using RapiDoc, ReDoc, or SwaggerUI
• CLI built-in, configured via arguments or environment variables
  • Set via e.g. -p 8000, --port=8000, or SERVICE_PORT=8000
• Generates OpenAPI JSON for access to a rich ecosystem of tools
  • Mocks with API Sprout
  • SDKs with OpenAPI Generator
  • CLIs with OpenAPI CLI Generator
  • And plenty more

This project was inspired by FastAPI, Gin, and countless others. Look at the benchmarks to see how Huma compares.

Logo & branding designed by Kari Taylor.

Concepts & Example

REST APIs are composed of operations against resources and can include descriptions of various inputs and possible outputs. For each operation you will typically provide info like:

• HTTP method & path (e.g. GET /items/{id})
• User-friendly description text
• Input path, query, or header parameters
• Input request body model, if appropriate
• Response header names and descriptions
• Response status code, content type, and output model

Huma uses standard Go types and a declarative API to capture those descriptions in order to provide a combination of a simple interface and idiomatic code leveraging Go's speed and strong typing.

Let's start by taking a quick look at a note-taking REST API. You can list notes, get a note's contents, create or update notes, and delete notes from an in-memory store. Each of the operations is registered with the router and descibes its inputs and outputs. You can view the full working example below:

package main

import (
	"net/http"
	"sync"
	"time"

	"github.com/danielgtaylor/huma"
)

// NoteSummary is used to list notes. It does not include the (potentially)
// large note content.
type NoteSummary struct {
	ID      string
	Created time.Time
}

// Note records some content text for later reference.
type Note struct {
	Created time.Time `readOnly:"true"`
	Content string
}

// We'll use an in-memory DB (a goroutine-safe map). Don't do this in
// production code!
var memoryDB = sync.Map{}

func main() {
	// Create a new router and give our API a title and version.
	r := huma.NewRouter(&huma.OpenAPI{
		Title:   "Notes API",
		Version: "1.0.0",
	})

	notes := r.Resource("/notes")
	notes.List("Returns a list of all notes",
		func() []*NoteSummary {
			// Create a list of summaries from all the notes.
			summaries := make([]*NoteSummary, 0)

			memoryDB.Range(func(k, v interface{}) bool {
				summaries = append(summaries, &NoteSummary{
					ID:      k.(string),
					Created: v.(*Note).Created,
				})
				return true
			})

			return summaries
		},
	)

	// Add an `id` path parameter to create a note resource.
	note := notes.With(huma.PathParam("id", "Note ID", &huma.Schema{
		Pattern: "^[a-zA-Z0-9._-]{1,32}$",
	}))

	notFound := huma.ResponseError(http.StatusNotFound, "Note not found")

	note.Put("Create or update a note",
		func(id string, n *Note) bool {
			// Set the created time to now and then save the note in the DB.
			n.Created = time.Now()
			memoryDB.Store(id, n)

			// Empty responses don't have a body, so you can just return `true`.
			return true
		},
	)

	note.With(notFound).Get("Get a note by its ID",
		func(id string) (*huma.ErrorModel, *Note) {
			if n, ok := memoryDB.Load(id); ok {
				// Note with that ID exists!
				return nil, n.(*Note)
			}

			return &huma.ErrorModel{
				Message: "Note " + id + " not found",
			}, nil
		},
	)

	note.With(notFound).Delete("Delete a note by its ID",
		func(id string) (*huma.ErrorModel, bool) {
			if _, ok := memoryDB.Load(id); ok {
				// Note with that ID exists!
				memoryDB.Delete(id)
				return nil, true
			}

			return &huma.ErrorModel{
				Message: "Note " + id + " not found",
			}, false
		},
	)

	// Run the app!
	r.Run()
}

Save this file as notes/main.go. Run it and then try to access the API with HTTPie-Go (or curl):

# Grab reflex to enable reloading the server on code changes:
$ go get github.com/cespare/reflex

# Grab HTTPie-go for making requests
$ go get -u github.com/nojima/httpie-go/cmd/ht

# Run the server (default host/port is 0.0.0.0:8888, see --help for options)
$ reflex -s go run notes/main.go

# Make some requests (in another tab)
$ ht put :8888/notes/test1 content="Some content for note 1"
HTTP/1.1 204 No Content
Date: Sat, 07 Mar 2020 22:22:06 GMT

$ ht put :8888/notes/test2 content="Some content for note 2"
HTTP/1.1 204 No Content
Date: Sat, 07 Mar 2020 22:22:06 GMT

# Parameter validation works too!
$ ht put :8888/notes/@bad content="Some content for an invalid note"
HTTP/1.1 400 Bad Request
Content-Length: 97
Content-Type: application/json; charset=utf-8
Date: Sat, 07 Mar 2020 22:22:06 GMT

{
    "errors": [
        "(root): Does not match pattern '^[a-zA-Z0-9._-]{1,32}$'"
    ],
    "message": "Invalid input"
}

# List all the notes
$ ht :8888/notes
HTTP/1.1 200 OK
Content-Length: 122
Content-Type: application/json; charset=utf-8
Date: Sat, 07 Mar 2020 22:22:06 GMT

[
    {
        "created": "2020-03-07T22:22:06-07:00",
        "id": "test1"
    },
    {
        "created": "2020-03-07T22:22:06-07:00",
        "id": "test2"
    }
]

The server works and responds as expected. There are also some neat extras built-in. If you go to http://localhost:8888/docs in a browser, you will see auto-generated interactive documentation:

The documentation is generated from the OpenAPI 3 spec file that is available at http://localhost:8888/openapi.json. You can also access this spec without running the server:

# Save the OpenAPI 3 spec to a file.
$ go run notes/main.go openapi notes.json

Combine the above with openapi-cli-generator and huma-build and you get the following out of the box:

• Small, efficient deployment Docker image with your service
• Auto-generated service documentation
• Auto-generated SDKs for any language
• Auto-generated cross-platform zero-dependency CLI

Documentation

Official Go package documentation can always be found at https://pkg.go.dev/github.com/danielgtaylor/huma. Below is an introduction to the various features available in Huma.

🐳 Hi there! I'm the happy Huma whale here to provide help. You'll see me leave helpful tips down below.

Resources

Huma APIs are composed of resources and sub-resources attached to a router. A resource refers to a unique URI on which operations can be performed. Huma resources can have dependencies, security requirements, parameters, response headers, and responses attached to them which are all applied to every operation and sub-resource.

r := huma.NewRouter(&huma.OpenAPI{Title: "Test", Version: "1.0.0"})

// Create a resource at a given path
notes := r.Resource("/notes")

// Create another resource that includes a path parameter: /notes/{id}
note := notes.With(huma.PathParam("id", "Note ID"))

// Create a sub-resource at /notes/{id}/likes
sub := note.SubResource("/likes")

The With(...) function is very powerful and can accept dependencies, security requirements, parameters, response headers, and response descriptions. It returns a copy of the resource with those values applied.

🐳 Resources should be nouns, and plural if they return more than one item. Good examples: /notes, /likes, /users, /videos, etc.

Operations

Operations perform an action on a resource using an HTTP method verb. The following verbs are available:

• Head
• List (alias for Get)
• Get
• Post
• Put
• Patch
• Delete

Operations can take dependencies, parameters, & request bodies and produce response headers and responses. These are each discussed in more detail below.

If you don't provide a response description, then one is generated for you based on the response type with the following rules:

• Boolean: If true, returns HTTP 204 No Content
• String: If not empty, returns HTTP 200 OK with content type text/plain
• Slice, map, struct pointer: If not nil, marshal to JSON and return HTTP 200 OK with content type application/json

If you need any customization beyond the above then you must provide a response description.

r := huma.NewRouter(&huma.OpenAPI{Title: "Test", Version: "1.0.0"})

// Create a resource
notes := r.Resource("/notes")

// Create the operation with an auto-generated response.
notes.Get("Get a list of all notes", func () []*NoteSummary {
	// Implementation goes here
})

// Manually provide the response. This is equivalent to the above.
notes.With(
	huma.ResponseJSON(http.StatusOK, "Success"),
).Get("Get a list of all notes", func () []*NoteSummary {
	// Implementation goes here
})

// The above idiom is common enough when needing to change response codes
// or allow certain response headers that there is a shortcut:
notes.
	JSON(http.StatusCreated, "Success", "expires").
	Get("Get a list of all notes", func () []*NoteSummary {
		// Implementation goes here
	})

Alternatively you can provide a *huma.Operation instance to the resource if you want more flexibility or prefer this style over chaining:

// Create the operation
notes.Operation(http.MethodGet, &huma.Operation{
	Description: "Get a list of all notes"
	Responses: []*huma.Response{
		huma.ResponseJSON(http.StatusOK, "List of notes", "expires"),
	},
	Handler: func () []*NoteSummary {
		// Implementation goes here
	}
})

🐳 Operations map an HTTP action verb to a resource. You might POST a new note or GET a user. Sometimes the mapping is less obvious and you can consider using a sub-resource. For example, rather than unliking a post, maybe you DELETE the /posts/{id}/likes resource.

Handler Functions

The basic structure of a Huma handler function looks like this, with most arguments being optional and dependent on the declaritively described operation:

func (deps..., params..., requestModel) (headers..., responseModels...)

Dependencies, parameters, headers, and models are covered in more detail in the following sections. For now this gives an idea of how to write handler functions based on the inputs and outputs of your operation.

For example, the most basic "Hello world" that takes no parameters and returns a greeting message might look like this:

func () string { return "Hello, world" }

Another example: you have an id parameter input and return a response model to be marshalled as JSON:

func (id string) *MyModel { return &MyModel{ID: id} }

🐳 Confused about what a handler should look like? Just run your service and it'll print out an approximate handler function when it panics.

Parameters

Huma supports three types of parameters:

• Required path parameters, e.g. /things/{thingId}
• Optional query string parameters, e.g. /things?q=filter
• Optional header parameters, e.g. X-MyHeader: my-value

Optional parameters require a default value.

Here is an example of an id parameter:

r.Resource("/notes",
	huma.PathParam("id", "Note ID"),
	huma.ResponseJSON(200, "Success"),
	huma.ResponseError(404, "Note was not found"),
).
Get("Get a note by its ID", func(id string) (*huma.ErrorModel, *Note) {
	// Implementation goes here
})

You can also declare parameters with additional validation logic:

huma.PathParam("id", "Note ID", &huma.Schema{
	MinLength: 1,
	MaxLength: 32,
})

Once a parameter is declared it will get parsed, validated, and then sent to your handler function. If parsing or validation fails, the client gets a 400-level HTTP error.

🐳 If a proxy is providing e.g. authentication or rate-limiting and exposes additional internal-only information then use the internal parameters like huma.HeaderParamInternal("UserID", "Parsed user from the auth system", "nobody"). Internal parameters are never included in the generated OpenAPI 3 spec or documentation.

Request & Response Models

Request and response models are just plain Go structs with optional tags to annotate additional validation logic for their fields. From the notes API example above:

// Note records some content text for later reference.
type Note struct {
	Created time.Time `readOnly:"true"`
	Content string
}

The Note struct has two fields which will get serialized to JSON. The Created field has a special tag readOnly set which means it will not get used for write operations like PUT /notes/{id}.

This struct provides enough information to create JSON Schema for the OpenAPI 3 spec. You can provide as much or as little information and validation as you like.

Request Model

Request models are used by adding a new input argument that is a pointer to a struct to your handler function as the last argument. For example:

r.Resource("/notes", huma.PathParam("id", "Note ID")).
	Put("Create or update a note",
		// Handler without an input body looks like:
		func(id string) bool {
			// Implementation goes here
		},

		// Handler with an input body looks like:
		func(id string, note *Note) bool {
			// Implementation goes here
		},
	)

The presence of the note *Note argument tells Huma to parse the request body and validate it against the generated JSON Schema for the Note struct.

Response Model

Response models are used by adding a response to the list of possible responses along with a new function return value that is a pointer to your struct. You can specify multiple different response models.

r.
	Resource("/notes",
		huma.ResponseJSON(http.StatusOK, "Success"),
		huma.ResponseError(http.NotFound, "Not found")).
	Get("Description", func() (*huma.ErrorModel, *Note) {
		// Implementation goes here
	})

Whichever model is not nil will get sent back to the client.

Empty responses, e.g. a 204 No Content or 304 Not Modified are also supported. Use huma.ResponseEmpty paired with a simple boolean to return a response without a body. Passing false acts like nil for models and prevents that response from being sent.

r.Resource("/notes",
	huma.ResponseEmpty(http.StatusNoContent, "This should have no body")).
Get("description", func() bool {
	return true
})
},

🐳 In some cases Huma can auto-generate a resonse model for you.

Model Tags

Go struct tags are used to annotate the model with information that gets turned into JSON Schema for documentation and validation.

The standard json tag is supported and can be used to rename a field and mark fields as optional using omitempty. The following additional tags are supported on model fields:

Tag	Description	Example
description	Describe the field	description:"Who to greet"
format	Format hint for the field	format:"date-time"
enum	A comma-separated list of possible values	enum:"one,two,three"
default	Default value	default:"123"
minimum	Minimum (inclusive)	minimum:"1"
exclusiveMinimum	Minimum (exclusive)	exclusiveMinimum:"0"
maximum	Maximum (inclusive)	maximum:"255"
exclusiveMaximum	Maximum (exclusive)	exclusiveMaximum:"100"
multipleOf	Value must be a multiple of this value	multipleOf:"2"
minLength	Minimum string length	minLength:"1"
maxLength	Maximum string length	maxLength:"80"
pattern	Regular expression pattern	pattern:"[a-z]+"
minItems	Minimum number of array items	minItems:"1"
maxItems	Maximum number of array items	maxItems:"20"
uniqueItems	Array items must be unique	uniqueItems:"true"
minProperties	Minimum number of object properties	minProperties:"1"
maxProperties	Maximum number of object properties	maxProperties:"20"
example	Example value	example:"123"
nullable	Whether null can be sent	nullable:"false"
readOnly	Sent in the response only	readOnly:"true"
writeOnly	Sent in the request only	writeOnly:"true"
deprecated	This field is deprecated	deprecated:"true"

Response Headers

Response headers must be defined before they can be sent back to a client. This includes several steps:

1. Describe the response header (name & description)
2. Specify which responses may send this header
3. Add the header to the handler function return values

For example:

r.Resource("/notes",
	huma.Header("expires", "Expiration date for this content"),
	huma.ResponseText(http.StatusOK, "Success", "expires")).
Get("description", func() (string, string) {
	expires := time.Now().Add(7 * 24 * time.Hour).MarshalText()
	return expires, "Hello!"
})

You can make use of named return values with a naked return to disambiguate complex functions:

func() (expires string, message string) {
	expires = time.Now().Add(7 * 24 * time.Hour).MarshalText()
	message = "Hello!"
	return
},

🐳 If you forget to declare a response header for a particular response and then try to set it when returning that response it will not be sent to the client and an error will be logged.

Dependencies

Huma includes a dependency injection system that can be used to pass additional arguments to operation handler functions. You can register global dependencies (ones that do not change from request to request) or contextual dependencies (ones that change with each request).

Global dependencies are created by just setting some value, while contextual dependencies are implemented using a function that returns the value of the form func (deps..., params...) (headers..., *YourType, error) where the value you want injected is of *YourType and the function arguments can be any previously registered dependency types or one of the hard-coded types:

• huma.ContextDependency() the current http.Request context (returns context.Context)
• huma.GinContextDependency() the current Gin request context (returns *gin.Context)
• huma.OperationDependency() the current operation (returns *huma.Operation)

// Register a new database connection dependency
db := &huma.Dependency{
	Value: db.NewConnection(),
}

// Register a new request logger dependency. This is contextual because we
// will print out the requester's IP address with each log message.
type MyLogger struct {
	Info: func(msg string),
}

logger := &huma.Dependency{
	Dependencies: []*huma.Dependency{huma.ContextDependency()},
	Value: func(c *gin.Context) (*MyLogger, error) {
		return &MyLogger{
			Info: func(msg string) {
				fmt.Printf("%s [ip:%s]\n", msg, c.Request.RemoteAddr)
			},
		}, nil
	},
}

// Use them in any handler by adding them to both `Depends` and the list of
// handler function arguments.
r.Resource("/foo").Operation(http.MethodGet, &huma.Operation{
	// ...
	Dependencies: []*huma.Dependency{db, logger},
	Handler: func(db *db.Connection, log *MyLogger) string {
		log.Info("test")
		item := db.Fetch("query")
		return item.ID
	}
})

🐳 Note that global dependencies cannot be functions. You can wrap them in a struct as a workaround if needed.

Custom Gin

You can create a Huma router instance with a custom Gin instance. This lets you set up custom middleware, CORS configurations, logging, etc.

// This is a shortcut:
r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Notes API",
	Version: "1.0.0",
})

// For this:
g := gin.New()
g.Use(huma.Recovery())
g.Use(huma.LogMiddleware(nil, nil))
g.Use(cors.Default())
g.NoRoute(huma.Handler404)
r := huma.NewRouterWithGin(g, &huma.OpenAPI{
	Title:   "Notes API",
	Version: "1.0.0",
})

Logging

Huma provides a Zap-based contextual structured logger built-in. You can access it via the huma.LogDependency() which returns a *zap.SugaredLogger. It requires the use of the huma.LogMiddleware(...), which is included by default.

r.Resource("/test",
	huma.LogDependency(),
	huma.ResponseText(http.StatusOK, "Successful")).
Get("Logger test", func(log *zap.SugaredLogger) string {
	log.Info("I'm using the logger!")
	return "Hello, world"
})

Customizing Logging

Logging is completely customizable.

// Create your own logger, or use the Huma built-in:
l, err := huma.NewLogger()
if err != nil {
	panic(err)
}

// Update the logger somehow with your custom logic.
l = l.With(zap.String("some", "value"))

// Set up the router with the default settings and your custom logger.
g := gin.New()
g.Use(gin.Recovery())
g.Use(cors.Default())
g.Use(huma.LogMiddleware(l, nil))
r := huma.NewRouterWithGin(g, &huma.OpenAPI{
	Title:   "Notes API",
	Version: "1.0.0",
})

Lazy-loading at Server Startup

You can register functions to run before the server starts, allowing for things like lazy-loading dependencies.

var db *mongo.Client

r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Example API",
	Version: "1.0.0",
})

r.PreStart(func() {
	// Connect to the datastore
	var err error
	db, err = mongo.Connect(context.Background(),
		options.Client().ApplyURI("..."))
})

🐳 This is especially useful for external dependencies and if any custom CLI commands are set up. For example, you may not want to require a database to run my-service openapi my-api.json.

Changing the Documentation Renderer

You can choose between RapiDoc, ReDoc, or SwaggerUI to auto-generate documentation. Simply set the documentation handler on the router:

r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Example API",
	Version: "1.0.0",
})

r.SetDocsHandler(huma.ReDocHandler)

🐳 Pass a custom handler function to have even more control for branding or browser authentication.

Custom OpenAPI Fields

You can set custom OpenAPI fields via the Extra field in the OpenAPI and Operation structs.

r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Example API",
	Version: "1.0.0",
	Extra: map[string]interface{}{
		"x-something": "some-value",
	},
})

Custom CLI Arguments

You can add additional CLI arguments, e.g. for additional logging tags. Use the AddGlobalFlag function along with the viper module to get the parsed value.

r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Example API",
	Version: "1.0.0",
})

// Add a long arg (--env), short (-e), description & default
r.AddGlobalFlag("env", "e", "Environment", "local")

r.Resource("/current_env").Text(http.StatusOK, "Success").Get(
	"Return the current environment",
	func() string {
		return viper.GetString("env")
	},
)

Then run the service:

$ go run yourservice.go --env=prod

🐳 Combine custom arguments with customized logger setup and you can easily log your cloud provider, environment, region, pod, etc with every message.

Custom CLI Commands

You can access the root cobra.Command via r.Root() and add new custom commands via r.Root().AddCommand(...). The openapi sub-command is one such example in the default setup.

🐳 You can also overwite the r.Root().Command to completely customize how you run the server.

Middleware

You can make use of any Gin-compatible middleware via the Use() router function.

r := huma.NewRouter(&huma.OpenAPI{
	Title:   "Example API",
	Version: "1.0.0",
})

r.Use(gin.Logger())

HTTP/2 Setup

TODO

How it Works

Huma's philosophy is to make it harder to make mistakes by providing tools that reduce duplication and encourage practices which make it hard to forget to update some code.

An example of this is how handler functions must declare all headers that they return and which responses may send those headers. You simply cannot return from the function without considering the values of each of those headers. If you set one that isn't appropriate for the response you return, Huma will let you know.

How does it work? Huma asks that you give up one compile-time static type check for handler function signatures and instead let it be a runtime startup check. It's simple enough that even the most basic unit test will invoke the runtime check, giving you most of the security you would from static typing.

Using a small amount of reflection, Huma can verify the function signatures, inject dependencies and parameters, and handle responses and headers as well as making sure that they all match the declared operation.

By strictly enforcing this runtime interface you get several advantages. No more out of date API description. No more out of date documenatation. No more out of date SDKs or CLIs. Your entire ecosystem of tooling is driven off of one simple backend implementation. Stuff just works.

More docs coming soon.

🐳 Thanks for reading!