add github.com/docker/docker dependency

vendor/github.com/docker/go-connections/sockets/tcp_socket.go

@@ -0,0 +1,22 @@
+// Package sockets provides helper functions to create and configure Unix or TCP sockets.
+package sockets
+
+import (
+	"crypto/tls"
+	"net"
+)
+
+// NewTCPSocket creates a TCP socket listener with the specified address and
+// the specified tls configuration. If TLSConfig is set, will encapsulate the
+// TCP listener inside a TLS one.
+func NewTCPSocket(addr string, tlsConfig *tls.Config) (net.Listener, error) {
+	l, err := net.Listen("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	if tlsConfig != nil {
+		tlsConfig.NextProtos = []string{"http/1.1"}
+		l = tls.NewListener(l, tlsConfig)
+	}
+	return l, nil
+}