add err handling and change order of resp dealing and nil judging

Signed-off-by: allencloud <allen.sun@daocloud.io>

client/request.go

@@ -85,6 +85,10 @@ func (cli *Client) sendClientRequest(ctx context.Context, method, path string, q
 	}
 
 	req, err := cli.newRequest(method, path, query, body, headers)
+	if err != nil {
+		return serverResp, err
+	}
+
 	if cli.proto == "unix" || cli.proto == "npipe" {
 		// For local communications, it doesn't matter what the host is. We just
 		// need a valid and meaningful host name. (See #189)
@@ -98,10 +102,6 @@ func (cli *Client) sendClientRequest(ctx context.Context, method, path string, q
 	}
 
 	resp, err := cancellable.Do(ctx, cli.transport, req)
-	if resp != nil {
-		serverResp.statusCode = resp.StatusCode
-	}
-
 	if err != nil {
 		if isTimeout(err) || strings.Contains(err.Error(), "connection refused") || strings.Contains(err.Error(), "dial unix") {
 			return serverResp, ErrConnectionFailed
@@ -110,6 +110,7 @@ func (cli *Client) sendClientRequest(ctx context.Context, method, path string, q
 		if !cli.transport.Secure() && strings.Contains(err.Error(), "malformed HTTP response") {
 			return serverResp, fmt.Errorf("%v.\n* Are you trying to connect to a TLS-enabled daemon without TLS?", err)
 		}
+
 		if cli.transport.Secure() && strings.Contains(err.Error(), "remote error: bad certificate") {
 			return serverResp, fmt.Errorf("The server probably has client authentication (--tlsverify) enabled. Please check your TLS client certification settings: %v", err)
 		}
@@ -117,6 +118,10 @@ func (cli *Client) sendClientRequest(ctx context.Context, method, path string, q
 		return serverResp, fmt.Errorf("An error occurred trying to connect: %v", err)
 	}
 
+	if resp != nil {
+		serverResp.statusCode = resp.StatusCode
+	}
+
 	if serverResp.statusCode < 200 || serverResp.statusCode >= 400 {
 		body, err := ioutil.ReadAll(resp.Body)
 		if err != nil {