A small and evil REST framework for Go
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Latest commit d72b2aa Jan 20, 2017 @ungerik docu


go-rest A small and evil REST framework for Go

Reflection, Go structs, and JSON marshalling FTW!

Download, build and run example:

go get github.com/ungerik/go-rest
go install github.com/ungerik/go-rest/example && example


Yes, the framework consists of only three functions: HandleGET, HandlePOST, RunServer.


Well, this package can be considered bad design because HandleGET and HandlePOST use dynamic typing to hide 36 combinations of handler function types to make the interface easy to use. 36 static functions would have been more lines of code but dramatic simpler in their individual implementations. So simple in fact, that there wouldn't be a point in abstracting them away in an extra framework. See this great talk about easy vs. simple: http://www.infoq.com/presentations/Simple-Made-Easy Rob Pike may also dislike this approach: https://groups.google.com/d/msg/golang-nuts/z4T_n4MHbXM/jT9PoYc6I1IJ So yes, this package can be called evil because it is an anti-pattern to all that is good and right about Go.

Why use it then? By maximizing dynamic code it is easy to use and reduces code. Yes, that introduces some internal complexity, but this complexity is still very low in absolute terms and thus easy to control and debug. The complexity of the dynamic code also does not spill over into the package users' code, because the arguments and results of the handler functions must be static typed and can't be interface{}.

Now let's have some fun:

HandleGET uses a handler function that returns a struct or string to create the GET response. Structs will be marshalled as JSON, strings will be used as body with auto-detected content type.

Format of GET handler:

func([url.Values]) ([struct|*struct|string][, error]) {}


type MyStruct struct {
	A in
	B string

rest.HandleGET("/data.json", func() *MyStruct {
	return &MyStruct{A: 1, B: "Hello World"}

rest.HandleGET("/index.html", func() string {
	return "<!doctype html><p>Hello World"

The GET handler function can optionally accept an url.Values argument and return an error as second result value that will be displayed as 500 internal server error if not nil.


rest.HandleGET("/data.json", func(params url.Values) (string, error) {
	v := params.Get("value")
	if v == "" {
		return nil, errors.New("Expecting GET parameter 'value'")
	return "value = " + v, nil

HandlePOST maps POST form data or a JSON document to a struct that is passed to the handler function. An error result from handler will be displayed as 500 internal server error message. An optional first string result will be displayed as a 200 response body with auto-detected content type.

Format of POST handler:

func([*struct|url.Values]) ([struct|*struct|string],[error]) {}


rest.HandlePOST("/change-data", func(data *MyStruct) (err error) {
	// save data
	return err

Both HandleGET and HandlePOST also accept one optional object argument. In that case handler is interpreted as a method of the type of object and called accordingly.


rest.HandleGET("/method-call", (*myType).MethodName, myTypeObject)