100 lines
2.0 KiB
Go
100 lines
2.0 KiB
Go
package main
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import (
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"context"
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"fmt"
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"net/http"
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"time"
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)
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const PORT = 8080
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func main() {
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server := NewServer(1 * time.Second)
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server.Handle(
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"/get-value",
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addValueToContext,
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handleGetValue,
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)
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if err := server.Listen(PORT); err != nil {
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panic(err)
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}
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fmt.Println("listening on :", PORT)
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}
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func handleGetValue(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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fmt.Println("starting handleGetValue")
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defer fmt.Println("finished executing handleGetNumber")
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message, err := executeHandleGetValue(r.Context(), r)
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if err != nil {
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w.Write([]byte(fmt.Sprintf("\nError happened: %s", err.Error())))
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fmt.Println("Error happened: ", err)
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return
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}
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w.Write([]byte(message))
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})
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}
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func executeHandleGetValue(ctx context.Context, r *http.Request) (string, error) {
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chanErr := make(chan error, 1)
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go func() {
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fmt.Println("executeHandleGetValue started")
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time.Sleep(2 * time.Second)
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// simulate errors
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shouldError := true
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if shouldError {
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chanErr <- fmt.Errorf("an error happened during goroutine")
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} else {
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chanErr <- nil
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}
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fmt.Println("executeHandleGetValue ended")
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}()
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select {
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case <-ctx.Done():
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<-chanErr
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return "", ctx.Err()
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case err := <-chanErr:
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return "finished successfully", err
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}
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}
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func addValueToContext(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// Add simple values
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ctx1 := context.WithValue(r.Context(), "number", 420)
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ctx2 := context.WithValue(ctx1, "sad_message", "RIP Toriyama :(")
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// Add a more complex one
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cs := ComplexStruct{
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question: "What is your favourite Dragon Ball character?",
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possibleAnswers: []string{
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"Goku",
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"Gohan",
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"Vegeta",
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"You get the idea zz",
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},
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}
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ctx3 := context.WithValue(ctx2, "complex_struct", cs)
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next.ServeHTTP(w, r.WithContext(ctx3))
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})
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}
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type ComplexStruct struct {
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question string
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possibleAnswers []string
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}
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