Terminate http request via header error code return or JSON response -

how can call multiple error return functions handlefunc?

i have found similar need in link: golang: terminating or aborting http request.

so, in cases, need return error response http error code, below (code taken link above):

http.handlefunc("/", func(w http.responsewriter, r *http.request) {    // examine incoming params    if !ok {    http.error(w, `invalid input params!`, http.statusbadrequest)     return           }     // normal api serving }) 

however, in cases need return json response web client:

http.handlefunc("/", func(w http.responsewriter, r *http.request) {     // examine incoming params     if !ok {         w.header().set("content-type", "application/json")         w.writeheader(http.statusbadrequest)         str := `{"result":"","error":"no valide var"}`         fmt.fprint(w, str)         return     }      // normal api serving }) 

question is: want place error handling part in seperate error function , passing type of error want present function parameter/method. don't know, how semantically.

so, in gist:

 if isjsonerror {     //call http function serve json error    }  if ishttperror {    //call http function serve http error } 

how can semantically? sorry in advance, if i'm not being clear. thank you!

p.s.: i've read following blogpost : http://blog.golang.org/error-handling-and-go

there section there called "simplifying repetitive error handling" - , it's cool need simplify multiple repetitive error handling , can't figure out how to.

the custom handler approach (as per blog post)—with func(w http.responsewriter, r *http.request) error signature way go. return &httperror{err, code} or &jsonerror{err, code} , have servehttp inspect , render appropriately. e.g.

type handler struct {     h func(http.responsewriter, *http.request) error }  func (h handler) servehttp(w http.responsewriter, r *http.request) {     // execute handler function     err := h.h(w, r)     if err != nil {         switch e := err.(type) {         case *htmlerror:              // render html response, calling e.err , e.code         case *jsonerror:              // render json response         default:              // handle other 'generic' errors don't inspect         }     } }  type htmlerror struct {     err error     code int }  func (e *htmlerror) error() string {     return e.err.error() }  type jsonerror struct {     err error     code int }  func (e *jsonerror) error() string {     return e.err.error() }  func somehandler(w http.responsewriter, r *http.request) error {     // examine incoming params     if !ok {         // returns enforced here - avoiding subtle bugs         return &httperror{errors.new("no good!"), http.statusbadrequest}     } } 

small plug: wrote blog post ways centralise error handling handlers similar example above.