103 lines
2.2 KiB
Go
103 lines
2.2 KiB
Go
package main
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import (
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"context"
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"fmt"
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"log"
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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 := &Server{}
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server.Handle("/get-value", addValueToContext, handleGetValue)
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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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log.Println("handleGetValue started")
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defer log.Println("handleGetNumber ended")
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ctx, cancelCtx := context.WithTimeout(r.Context(), 8*time.Second)
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defer cancelCtx()
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err := someLongAction(ctx)
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if err != nil {
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w.Write([]byte(fmt.Sprintf("\n%s - Error happened: %s", t(), err.Error())))
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log.Println("Error happened: ", err)
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return
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}
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w.Write([]byte(fmt.Sprintf("%s -- operation finished successfully", t())))
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})
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}
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func someLongAction(ctx context.Context) error {
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log.Println("someLongAction started")
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defer log.Println("someLongAction ended")
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select {
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case err := <-simulatingOperation():
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return err
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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func simulatingOperation() chan error {
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log.Println("simlatingOperation started")
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defer log.Println("simlatingOperation ended")
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chanErr := make(chan error, 1)
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go func() {
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log.Println("goroutine in simulatingOperation started")
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defer log.Println("goroutine in simulatingOperation ended")
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time.Sleep(5 * time.Second)
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chanErr <- fmt.Errorf("something terrible happened, PLEASE HELP!")
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}()
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return chanErr
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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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func t() string {
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return time.Now().Format("15:06:05")
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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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