Add ProxyFromEnvironment enables client via proxy.

Signed-off-by: Anders Janmyr <anders@janmyr.com>

api/client/cli.go

@@ -155,6 +155,7 @@ func NewDockerCli(in io.ReadCloser, out, err io.Writer, key libtrust.PrivateKey,
 
 	// The transport is created here for reuse during the client session
 	tr := &http.Transport{
+		Proxy:           http.ProxyFromEnvironment,
 		TLSClientConfig: tlsConfig,
 	}