move to newNetDialerFunc

client.go

@@ -246,19 +246,7 @@ func (d *Dialer) DialContext(ctx context.Context, urlStr string, requestHeader h
 		defer cancel()
 	}
 
-	var netDial netDialerFunc
+	netDial := newNetDialerFunc(u.Scheme, d.NetDial, d.NetDialContext, d.NetDialTLSContext)
-	switch {
-	case u.Scheme == "https" && d.NetDialTLSContext != nil:
-		netDial = d.NetDialTLSContext
-	case d.NetDialContext != nil:
-		netDial = d.NetDialContext
-	case d.NetDial != nil:
-		netDial = func(ctx context.Context, net, addr string) (net.Conn, error) {
-			return d.NetDial(net, addr)
-		}
-	default:
-		netDial = (&net.Dialer{}).DialContext
-	}
 
 	// If needed, wrap the dial function to connect through a proxy.
 	if d.Proxy != nil {

proxy.go

@@ -16,6 +16,26 @@ import (
 	"strings"
 )
 
+func newNetDialerFunc(
+	scheme string,
+	netDial func(network, addr string) (net.Conn, error),
+	netDialContext func(ctx context.Context, network, addr string) (net.Conn, error),
+	netDialTLSContext func(ctx context.Context, network, addr string) (net.Conn, error),
+) netDialerFunc {
+	switch {
+	case scheme == "https" && netDialTLSContext != nil:
+		return netDialTLSContext
+	case netDialContext != nil:
+		return netDialContext
+	case netDial != nil:
+		return func(ctx context.Context, net, addr string) (net.Conn, error) {
+			return netDial(net, addr)
+		}
+	default:
+		return (&net.Dialer{}).DialContext
+	}
+}
+
 type netDialerFunc func(ctx context.Context, network, addr string) (net.Conn, error)
 
 func (fn netDialerFunc) Dial(network, addr string) (net.Conn, error) {