Adding example of HTTP server using context.Context

examples/context-in-http-servers/context-in-http-servers.go

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+// In the previous example we looked at setting up a simple
+// [HTTP server](http-servers). HTTP servers are useful for
+// demonstrating the usage of `context.Context` for
+// controlling cancellation.
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"time"
+)
+
+func hello(w http.ResponseWriter, req *http.Request) {
+	// A `context.Context` is created for each request by
+	// the `net/http` machinery, and is available with
+	// the `Context()` method.
+	ctx := req.Context()
+	fmt.Println("server: hello handler started")
+	defer fmt.Println("server: hello handler ended")
+
+	// Wait for 3 seconds before sending a reply to the
+	// client. This could simulate some work the server is
+	// doing. While working, keep an eye on the context's
+	// `Done()` channel for a signal that we should cancel
+	// the work and return as soon as possible.
+	select {
+	case <-time.After(3 * time.Second):
+		fmt.Fprintf(w, "hello\n")
+	case <-ctx.Done():
+		err := ctx.Err()
+		fmt.Println("server:", err)
+		internalError := http.StatusInternalServerError
+		http.Error(w, err.Error(), internalError)
+	}
+}
+
+func main() {
+	// As before, we register our handler on the "/hello"
+	// route, and start serving.
+	http.HandleFunc("/hello", hello)
+	http.ListenAndServe(":8090", nil)
+}

examples/context-in-http-servers/context-in-http-servers.hash

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+4ec814bf1b01bf71fb95007cad39586ad87e3fb6
+k3vHfk-r3EE

examples/context-in-http-servers/context-in-http-servers.sh

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+# Run the server in the background.
+$ go run context-in-http-servers.go &
+
+# Simulate a client request to `/hello`, hitting
+# Ctrl+C shortly after starting to signal
+# cancellation.
+$ curl localhost:8090/hello
+server: hello handler started
+^C
+server: context canceled
+server: hello handler ended