From 2afbbb3400b076b9319833296dcf28949142dfe6 Mon Sep 17 00:00:00 2001
From: Jeff Mitchell <jeffrey.mitchell@gmail.com>
Date: Fri, 27 Oct 2017 14:08:30 -0400
Subject: [PATCH] Only call ConfigureTransport if "h2" is not already in
 NextProtos.

Fixes #3435
---
 api/client.go      | 15 +++++++++++++--
 api/client_test.go | 13 +++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/api/client.go b/api/client.go
index 6e0aa18eea87..d801c4397571 100644
--- a/api/client.go
+++ b/api/client.go
@@ -282,8 +282,19 @@ func NewClient(c *Config) (*Client, error) {
 	}
 
 	if tp, ok := c.HttpClient.Transport.(*http.Transport); ok {
-		if err := http2.ConfigureTransport(tp); err != nil {
-			return nil, err
+		if tcc := tp.TLSClientConfig; tcc != nil {
+			var found bool
+			for _, proto := range tcc.NextProtos {
+				if proto == "h2" {
+					found = true
+					break
+				}
+			}
+			if !found {
+				if err := http2.ConfigureTransport(tp); err != nil {
+					return nil, err
+				}
+			}
 		}
 	}
 
diff --git a/api/client_test.go b/api/client_test.go
index 3bc866b157b2..a11763411277 100644
--- a/api/client_test.go
+++ b/api/client_test.go
@@ -213,3 +213,16 @@ func TestClientNonTransportRoundTripper(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestClone(t *testing.T) {
+	client1, err1 := NewClient(nil)
+	if err1 != nil {
+		t.Fatalf("NewClient failed: %v", err1)
+	}
+	client2, err2 := client1.Clone()
+	if err2 != nil {
+		t.Fatalf("Clone failed: %v", err2)
+	}
+
+	_ = client2
+}