In program bellow I have two routers. One is working at localhost:3000 and acts like a public access point. It also may send requests with data to another local address which is localhost:8000 where data is being processed. Second router is working at localhost:8000 and handles processing requests for the first router.
Problem
The first router sends a request with context to the second using http.NewRequestWithContext() function. The value is being added to the context and the context is added to request. When request arrives to the second router it does not have value that was added previously.
Some things like error handling are not being written to not post a wall of code here.
package main
import (
"bytes"
"context"
"net/http"
"github.com/go-chi/chi"
"github.com/go-chi/chi/middleware"
)
func main() {
go func() {
err := http.ListenAndServe(
"localhost:3000",
GetDataAndSolve(),
)
if err != nil {
panic(err)
}
}()
go func() {
err := http.ListenAndServe( // in GetDataAndSolve() we send requests
"localhost:8000", // with data for processing
InternalService(),
)
if err != nil {
panic(err)
}
}()
// interrupt := make(chan os.Signal, 1)
// signal.Notify(interrupt, syscall.SIGTERM, syscall.SIGINT)
// <-interrupt // just a cool way to close the program, uncomment if you need it
}
func GetDataAndSolve() http.Handler {
r := chi.NewRouter()
r.Use(middleware.Logger)
r.Get("/tasks/str", func(rw http.ResponseWriter, r *http.Request) {
// receiving data for processing...
taskCtx := context.WithValue(r.Context(), "str", "strVar") // the value is being
postReq, err := http.NewRequestWithContext( // stored to context
taskCtx, // context is being given to request
"POST",
"http://localhost:8000/tasks/solution",
bytes.NewBuffer([]byte("something")),
)
postReq.Header.Set("Content-Type", "application/json") // specifying for endpoint
if err != nil { // what we are sending
return
}
resp, err := http.DefaultClient.Do(postReq) // running actual request
// pls, proceed to Solver()
// do stuff to resp
// also despite arriving to middleware without right context
// here resp contains a request with correct context
})
return r
}
func Solver(next http.Handler) http.Handler { // here we end up after sending postReq
return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
if r.Context().Value("str").(string) == "" {
return // the request arrive without "str" in its context
}
ctxWithResult := context.WithValue(r.Context(), "result", mockFunc(r.Context()))
next.ServeHTTP(rw, r.Clone(ctxWithResult))
})
}
func InternalService() http.Handler {
r := chi.NewRouter()
r.Use(middleware.Logger)
r.With(Solver).Post("/tasks/solution", emptyHandlerFunc)
return r
}
