Please, I searched this a lot and after not been able to find, I am writing and not that I didn't try to search all over first. Couldn't get the right answer. I even tried to check Revel's function and couldn't get the answer from there as well.
When I run this program I get this error for line
./test.go:11: use of package http without selector
This error points at the line below where I have written
*http
inside the struct
Confusing part is that with test and dot I even get auto complete with VIM. So I don't know why is the error. Is it that it has to be somewhat like
*(net/http)
or something like that ?
package main
import (
"fmt"
"net/http"
)
type HandleHTTP struct {
*http
}
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Path is %s", r.URL.Path[1:])
}
func main() {
test := HandleHTTP{}
test.http.HandleFunc("/", handler)
test.http.ListenAndServe(":8080", nil)
}
If you want to have two or more instances serving from different ports you need to spin up two, or more, server. Would something like this, perhaps, work for you?
package main
import (
"fmt"
"net/http"
)
type HandleHTTP struct {
http *http.Server
}
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Path is %s", r.URL.Path[1:])
}
func main() {
mux1 := http.NewServeMux()
mux1.HandleFunc("/", handler)
test1 := HandleHTTP{http:&http.Server{Addr:":8081", Handler:mux1}}
mux2 := http.NewServeMux()
mux2.HandleFunc("/", handler)
test2 := HandleHTTP{http:&http.Server{Addr:":8082", Handler:mux2}}
// run the first one in a goroutine so that the second one is executed
go test1.http.ListenAndServe()
test2.http.ListenAndServe()
}
Related
I am making an api and used swaggo/swag to build a swagger interface. Previously, I used the net/http package, and everything was working fine.
I switched to julienschmidt/httprouter, but I don't manage to make the swagger interface work again. Here is my code
package main
import (
"fmt"
"log"
"net/http"
"github.com/julienschmidt/httprouter"
httpSwagger "github.com/swaggo/http-swagger"
)
func main() {
router := httprouter.New()
router.ServeFiles("/api/doc/static/*filepath", http.Dir("api/swagger/static"))
router.HandlerFunc(http.MethodGet, "/api/doc/index.html", swaggerHandler)
// router.HandlerFunc(http.MethodGet, "/api/doc", swaggerHandler)
fmt.Println("Server on port 8080")
log.Fatal(http.ListenAndServe(":8080", router))
}
func swaggerHandler(w http.ResponseWriter, r *http.Request) {
swaggerFileUrl := "http://localhost:8080/api/doc/static/swagger.json"
handler := httpSwagger.Handler(httpSwagger.URL(swaggerFileUrl))
handler.ServeHTTP(w, r)
}
I checked if swaggerFileUrl variable is correct, and I am able to access the json file with this url. The interface is a complete blank page titled "Swagger UI". Because the title is replaced, I am assuming, that something happened, but I don't know if the issue comes from httpSwagger or httprouter.
Edit: Issue is caused because javascript files loading the interface are not present. See this github issue
You can do it like this:
routes := httprouter.New()
routes.GET("/doc/:any", swaggerHandler)
func swaggerHandler(res http.ResponseWriter, req *http.Request, p httprouter.Params) {
httpSwagger.WrapHandler(res, req)
}
Do not forget import doc files
import (
_ "example.project/docs"
)
I'm trying to access a controller from main.go but I'm getting the following error:
./main.go:34:28: cannot refer to unexported name controllers.getUserDetails
./main.go:34:28: undefined: controllers.getUserDetails
here's a snippet of my main.go, I've removed some extra code
package main
import (
"net/http"
"os"
"log"
"github.com/urfave/negroni"
"github.com/gorilla/mux"
"github.com/joho/godotenv"
"Go-Social/controllers"
)
func main() {
router := mux.NewRouter()
UserRouter := router.PathPrefix("/api/user").Subrouter()
UserRouter.HandleFunc("", controllers.getUserDetails).Methods("GET")
env := os.Getenv("GO_ENV")
if "" == env {
env = "Development"
}
// appending middlewares
server := negroni.Classic()
// router handler with negroni
server.UseHandler(router)
// starting server
server.Run(":" + os.Getenv(env + "_PORT"))
}
my controller.go file
package controllers
import (
"net/http"
"fmt"
)
func getUserDetails(w http.ResponseWriter, r *http.Request) {
fmt.Println("here")
message := "Hello World"
w.Write([]byte(message))
}
Please Help I'm new to Go. Thanks in advance.
to use a function from another package, you need to export it (GetUserDetails)
as said here
An identifier may be exported to permit access to it from another package
func GetUserDetails(w http.ResponseWriter, r *http.Request) {
fmt.Println("here")
message := "Hello World"
w.Write([]byte(message))
}
Since the getUserDetails function is in another package it cannot be accessed. Only functions starting with capital letter can be accessed. That's how encapsulation works in Go.
func GetUserDetails(w http.ResponseWriter, r *http.Request) {
fmt.Println("here")
message := "Hello World"
w.Write([]byte(message))
}
So in your main:
UserRouter.HandleFunc("", controllers.GetUserDetails).Methods("GET")
Language like Java, enCAPSulation in class-based OOP is achieved through private and public class variables / methods.
In Go, encapsulation is achieved on a package level.
In other words, in Go, starting with capital letter for any package object (type, variable or function) will allow you to access it from another package.
I created in the example at the bottom a little server which is running on port 3000. You can access it over "htto://localhost:3000/time". The whole Request is covered with two middlewares. First "cancelHandler" and Second "otherHandler" is called - which is responding with some dummy data after 4 seconds.
To my problem: When i request the page in a browser and then cancel the request (before the 4sec). The server is still handling the goroutine/request in the background. I spent already hours to find a solution on google but i can just not wrap my head around the context. (context.WithCancel()) I get that i have to create a chan and listen to it but how does this work with the requests. thats already a goroutine, do i have to create another goroutine in the request/goroutine? Also another question is, should i really use Context for that or is there an easier solution with the cancelNotifier?
Maybe someone can describe it for me and others which maybe have the same understanding problem.
Solution should be that the cancel Handler is stopping the goroutine/request, when the browser cancels the request.
Thank you very much for your time!
package main
import (
"log"
"net/http"
"time"
"fmt"
)
func otherHandler(format string) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
time.Sleep(time.Duration(4)*time.Second)
tm := time.Now().Format(format)
w.Write([]byte("The time is: " + tm))
fmt.Println("response:", "The time is: "+tm)
}
return http.HandlerFunc(fn)
}
func cancelHandler(h http.Handler) http.Handler {
fn := func(w http.ResponseWriter, r *http.Request) {
fmt.Println("start: called cancelHandler")
h.ServeHTTP(w, r)
fmt.Println("end: called cancelHandler")
}
return http.HandlerFunc(fn)
}
func main() {
mux := http.NewServeMux()
th := otherHandler(time.RFC1123)
mux.Handle("/time", cancelHandler(th))
log.Println("Listening...")
http.ListenAndServe(":3000", mux)
}
The only way to "stop" a function is to return from it. Thus, time.Sleep cannot be interrupted. Use a select statement instead:
package main
import (
"fmt"
"net/http"
"time"
)
func main() {
http.ListenAndServe(":3000", otherHandler(time.RFC1123))
}
func otherHandler(format string) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
select {
case <-time.After(4 * time.Second):
// time's up
case <-r.Context().Done():
// client gave up
return
}
tm := time.Now().Format(format)
w.Write([]byte("The time is: " + tm))
fmt.Println("response:", "The time is: "+tm)
}
}
In general, check the request context (or one that is derived from it) in strategic places. If the context is canceled, don't proceed any further and return.
I am trying to pass string to handler in given example.
package main
import (
"fmt"
"net/http"
)
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hi there, I love %s!", r.URL.Path[1:])
}
func main() {
http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)
}
Here is what i tried but it throws an error as it expects regular number of arguments:
package main
import (
"fmt"
"net/http"
)
func handler(w http.ResponseWriter, r *http.Request, s *string) {
fmt.Fprintf(w, "Hi there, I love %s!", *s)
}
func main() {
files := "bar"
http.HandleFunc("/", handler(&files))
http.ListenAndServe(":8080", nil)
}
I'm a little unclear on what you're trying to do, but based off what you said, why not try to encapsulate the data you want to pass in like this:
package main
import (
"fmt"
"net/http"
)
type FilesHandler struct {
Files string
}
func (fh *FilesHandler) handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hi there, I love %s!", fh.Files)
}
func main() {
myFilesHandler := &FilesHandler{Files: "bar"}
http.HandleFunc("/", myFilesHandler.handler)
http.ListenAndServe(":8080", nil)
}
This provides a little more granular control of what you make available to your Handler.
There are lots of options here, you could:
Use a closure to set state for the enclosed handler
Use a method on a struct for the handler, and set global state there
Use the request context to store a value, then get it out
Use a package global to store the value
Write your own router with a new signature (not as complex as it sounds, but probably not a good idea)
Write a helper function to do things like extract params from the url
It depends what s is really - is it a constant, is it based on some state, does it belong in a separate package?
One of ways is to store data in global variable:
package main
import (
"fmt"
"net/http"
)
var replies map[string]string
func handler1(w http.ResponseWriter, r *http.Request) {
r.ParseForm()
question := r.FormValue("question")
var answer string
var ok bool
if answer, ok = replies[question]; !ok {
answer = "I have no answer for this"
}
fmt.Fprintf(w, "Hi there, I love %s! My answer is: %s", question, answer)
}
func main() {
//files := "bar"
replies = map[string]string{
"UK": "London",
"FR": "Paris",
}
http.HandleFunc("/", handler1)
http.ListenAndServe(":8080", nil)
}
Here for brevity I've commented out files and put data as is into the map. You may read the file and put them there.
Usage with CURL:
$ curl -X POST 127.0.0.1:8080/ -d "question=FR"
Hi there, I love FR! My answer is: Paris
$ curl -X POST 127.0.0.1:8080/ -d "question=US"
Hi there, I love US! My answer is: I have no answer for this
I want create two http servers into one golang app. Example:
package main
import (
"io"
"net/http"
)
func helloOne(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "Hello world one!")
}
func helloTwo(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "Hello world two!")
}
func main() {
// how to create two http server instatce?
http.HandleFunc("/", helloOne)
http.HandleFunc("/", helloTwo)
go http.ListenAndServe(":8001", nil)
http.ListenAndServe(":8002", nil)
}
How to create two http server instance and add handlers for them?
You'll need to create separate http.ServeMux instances. Calling http.ListenAndServe(port, nil) uses the DefaultServeMux (i.e. shared). The docs for this are here: http://golang.org/pkg/net/http/#NewServeMux
Example:
func main() {
r1 := http.NewServeMux()
r1.HandleFunc("/", helloOne)
r2 := http.NewServeMux()
r2.HandleFunc("/", helloTwo)
go func() { log.Fatal(http.ListenAndServe(":8001", r1))}()
go func() { log.Fatal(http.ListenAndServe(":8002", r2))}()
select {}
}
Wrapping the servers with log.Fatal will cause the program to quit if one of the listeners doesn't function. If you wanted the program to stay up if one of the servers fails to start or crashes, you could err := http.ListenAndServe(port, mux) and handle the error another way.