Allow to bind chartmuseum to a specific interface

The new config option "listen.host" ("--listen-host", "LISTEN_HOST") may
be used to bind  chartmuseum to a specific interface rather than 0.0.0.0.

Default is 0.0.0.0 to stick with current behaviour.

Fixes #255

cmd/chartmuseum/main.go

@@ -107,7 +107,7 @@ func cliHandler(c *cli.Context) {
 		crash(err)
 	}
 
-	server.Listen(conf.GetInt("port"))
+	server.Listen(conf.GetString("listen.host"), conf.GetInt("port"))
 }
 
 func backendFromConfig(conf *config.Config) storage.Backend {

pkg/chartmuseum/router/router.go

@@ -163,13 +163,13 @@ func NewRouter(options RouterOptions) *Router {
 	return router
 }
 
-func (router *Router) Start(port int) {
+func (router *Router) Start(host string, port int) {
 	router.Logger.Infow("Starting ChartMuseum",
-		"port", port,
+		"host", host, "port", port,
 	)
 
 	server := http.Server{
-		Addr:         fmt.Sprintf(":%d", port),
+		Addr:         fmt.Sprintf("%s:%d", host, port),
 		Handler:      router,
 		ReadTimeout:  router.ReadTimeout,
 		WriteTimeout: router.WriteTimeout,

pkg/chartmuseum/server.go

@@ -73,7 +73,7 @@ type (
 
 	// Server is a generic interface for web servers
 	Server interface {
-		Listen(port int)
+		Listen(host string, port int)
 	}
 )
 

pkg/chartmuseum/server/multitenant/server.go

@@ -147,8 +147,8 @@ func NewMultiTenantServer(options MultiTenantServerOptions) (*MultiTenantServer,
 }
 
 // Listen starts the router on a given port
-func (server *MultiTenantServer) Listen(port int) {
-	server.Router.Start(port)
+func (server *MultiTenantServer) Listen(host string, port int) {
+	server.Router.Start(host, port)
 }
 
 func (server *MultiTenantServer) genIndex() {

pkg/config/vars.go

@@ -739,6 +739,15 @@ var configVars = map[string]configVar{
 			EnvVar: "ENFORCE_SEMVER2",
 		},
 	},
+	"listen.host": {
+		Type:    stringType,
+		Default: "0.0.0.0",
+		CLIFlag: cli.StringFlag{
+			Name:   "listen-host",
+			Usage:  "specifies the host to listen on",
+			EnvVar: "LISTEN_HOST",
+		},
+	},
 }
 
 func populateCLIFlags() {