add dialcontext experiment

experiments/dialcontext/dialcontext.go

@@ -0,0 +1,72 @@
+// dialcontext is a program to investigate whether an http request's context is passed through to
+// the DialContext function on a http.Transport
+
+package main
+
+import (
+	"context"
+	"crypto/tls"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/alexflint/go-arg"
+)
+
+type contextKey string
+
+var fooKey contextKey = "dialcontext.foo"
+
+func Main() error {
+	ctx := context.Background()
+
+	var args struct{}
+	arg.MustParse(&args)
+
+	// first construct an http transport
+	transport := http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
+			log.Printf("at dialcontext, got value %q", ctx.Value(fooKey))
+			return net.Dial(network, address)
+		},
+		ForceAttemptHTTP2:     true,
+		MaxIdleConns:          5,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+		TLSClientConfig:       &tls.Config{InsecureSkipVerify: true},
+	}
+
+	// now make a context containing a foo key
+	ctx = context.WithValue(ctx, fooKey, "hello dialcontext!")
+
+	// now make an ordinary http request
+	req, err := http.NewRequest("GET", "https://www.monasticacademy.org", nil)
+	if err != nil {
+		return err
+	}
+
+	// add the context to the request
+	req = req.WithContext(ctx)
+
+	// send the request
+	_, err = transport.RoundTrip(req)
+	if err != nil {
+		return err
+	}
+
+	log.Println("done")
+	return nil
+}
+
+func main() {
+	log.SetOutput(os.Stdout)
+	log.SetFlags(0)
+	err := Main()
+	if err != nil {
+		log.Fatal(err)
+	}
+}