Minimal HTTP API go library

Minimal is a fast & simple HTTP API library. It will automatically marshal JSON payloads to/from your request and response structs. It follows RFC7807 standard for returning useful problem details.

This library focuses on happy path to minimize code. For more complex use cases, we recommend sticking to a larger web framework.

This library requires Go 1.18 to work as it utilizes generics.

This library was forked from

Let’s keep this library minimal, please send PRs to delete unnecessary code.


Basic Example

package main

import (

  min ""

type GreetRequest struct {
  Name string `path:"name"`         // Get name from the URL path.
  Age  int    `header:"X-User-Age"` // Get age from HTTP header.

type GreetResponse struct {
  // Remember to add tags for automatic marshalling
  Greeting string `json:"data"`

func Greet(ctx context.Context, req GreetRequest) (*GreetResponse, error) {
  if req.Name == "" {
    return nil, min.ProblemValid(map[string]string{
      "name": "required",
  res := &GreetResponse{
    Greeting: fmt.Sprintf("Hello %s, you're %d years old.", req.Name, req.Age),

  return res, nil

func Pong(context.Context, min.Empty) (string, error) {
  return "pong", nil

func main() {
  r := min.New(nil)
  r.Get("/ping", min.H(Pong)) // Handlers are wrapped with `minimal.H`.
  r.Post("/greet/:name", min.H(Greet))


Minimal is configured by passing in the Config struct to minimal.New.

r := min.New(&min.Config{
  ProblemTypeUrlFormat: "",
  ProblemInstanceFunc: func(_ context.Context) string {
    return fmt.Sprintf("", time.Now().UnixMilli())


The format for the problem details type URI. See RFC7807


A function for generating a unique trace URI. Defaults to a timestamp. See RFC7807

Form (input only)

MIME: application/x-www-form-urlencoded, multipart/form-data

Parses form data requests. Use the form tag in your request struct.

Request parsing

Automatically unmarshals values from headers, URL query, URL path & request body into your request struct.

type MyRequest struct {
  // Get from the URL path.
  ID int64 `path:"id"`

  // Get from the URL query.
  Filter string `query:"filter"`

  // Get from the JSON, YAML, XML or form body.
  Content float64 `form:"bar" json:"bar"`

  // Get from the HTTP header.
  Lang string `header:"Accept-Language"`

Please note that using a pointer as the request type negatively affects performance.

Customize Response

Implement the StatusCoder and Headerer interfaces to customise headers and response codes.

type MyResponse struct {
  Foo  string `json:"foo"`

// Set a custom HTTP response code.
func (nr *MyResponse) StatusCode() int {
  return 201

// Add custom headers to the response.
func (nr *MyResponse) Header() http.Header {
  header := http.Header{}
  header.Set("foo", "bar")
  return header

Problem Details

Implement the Problemer to customize your error problem details. Or use the many built in problems:

return nil, min.ProblemUnexpected(e)
// or
return nil, min.ProblemNotFound()
// or
return nil, min.ProblemPermit(username)
// or
return nil, min.ProblemValid(map[string]string{
  "name": "required",
// or
return nil, min.ProblemRule("item is on backorder")
// or
return nil, min.ProblemOld()


You can create sub-routers using the Group function:

r := min.New(nil)
sub := r.Group("/api")


Minimal uses the standard http middleware format of func(http.RequestHandler) http.RequestHandler.

For example:

func loggingMiddleware(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request)  {

It is registered on a router using Use e.g.

r := min.New(nil)
r.Post("/", min.H(handler))

Middleware registered on a group only applies to routes in that group and child groups.

r := min.New(nil)
r.Get("/login", min.H(loginHandler))
r.Use(loggingMiddleware) // applied to all routes

api := r.Group("/api")
api.Get("/hello", min.H(helloHandler))
api.Use(authMiddleware) // applied to routes `/api/hello` and `/api/v2/bye`

v2 := api.Group("/v2")
v2.Get("/bye", min.H(byeHandler))
v2.Use(corsMiddleware) // only applied to `/api/v2/bye`

To pass values from the middleware to the handler extend the context e.g.

func myMiddleware(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request)  {
    ctx := context.WithValue(r.Context(), ContextUserKey, "my_user")
    next.ServeHTTP(w, r.WithContext(ctx))

This can now be accessed in the handler:

user := ctx.Value(ContextUserKey).(string)


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