Disable BGP functionality on Windows since gobgp does not support this. (#919)

Update README

Author: nathanejohnson

README.md

@@ -82,9 +82,10 @@ It supports ([Full feature list](https://fabiolb.net/feature/))
 * [Prometheus](https://fabiolb.net/feature/metrics/),
 * [Circonus](https://fabiolb.net/feature/metrics/),
 * [Graphite](https://fabiolb.net/feature/metrics/),
-* [StatsD](https://fabiolb.net/feature/metrics/) and
-* [DataDog](https://fabiolb.net/feature/metrics/) metrics
-* [WebUI](https://fabiolb.net/feature/web-ui/)
+* [StatsD](https://fabiolb.net/feature/metrics/),
+* [DataDog](https://fabiolb.net/feature/metrics/) for metrics,
+* [WebUI](https://fabiolb.net/feature/web-ui/) and
+* [Advertising BGP anycast addresses](https://fabiolb.net/feature/bgp/) on non-windows platforms.
 
 [Watch](https://www.youtube.com/watch?v=gf43TcWjBrE&list=PL81sUbsFNc5b-Gd59Lpz7BW0eHJBt0GvE&index=1)
 Kelsey Hightower demo Consul, Nomad, Vault and fabio at HashiConf EU 2016.

bgp/bgp.go bgp/bgp_nonwindows.gobgp/bgp.go renamed to bgp/bgp_nonwindows.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package bgp
 
 import (

bgp/bgp_test.go bgp/bgp_nonwindows_test.gobgp/bgp_test.go renamed to bgp/bgp_nonwindows_test.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package bgp
 
 import (

bgp/bgp_windows.go

@@ -0,0 +1,22 @@
+package bgp
+
+import (
+	"errors"
+	"github.com/fabiolb/fabio/config"
+)
+
+type BGPHandler struct{}
+
+var ErrNoWindows = errors.New("cannot run bgp on windows")
+
+func NewBGPHandler(config *config.BGP) (*BGPHandler, error) {
+	return nil, ErrNoWindows
+}
+
+func (bgph *BGPHandler) Start() error {
+	return ErrNoWindows
+}
+
+func ValidateConfig(config *config.BGP) error {
+	return ErrNoWindows
+}

docs/content/feature/bgp.md

@@ -3,6 +3,10 @@ title: "BGP"
 since: "1.6.3"
 ---
 
+NOTE: This feature does not work on Windows at present since the gobgp project
+does not support windows.
+
+
 This feature integrates the functionality of [gobgpd](https://github.com/osrg/gobgp)
 with fabio.  This is particularly useful in the scenario where we are using
 anycast IP addresses and want to dynamically advertise to upstream routers