add RegisterCheck web server option for internal health checks

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

web/options.go

@@ -25,6 +25,9 @@ type Options struct {
 	RegisterTTL      time.Duration
 	RegisterInterval time.Duration
 
+	// RegisterCheck runs a check function before registering the service
+	RegisterCheck func(context.Context) error
+
 	Server  *http.Server
 	Handler http.Handler
 
@@ -62,6 +65,10 @@ func newOptions(opts ...Option) Options {
 		o(&opt)
 	}
 
+	if opt.RegisterCheck == nil {
+		opt.RegisterCheck = DefaultRegisterCheck
+	}
+
 	return opt
 }
 
@@ -225,3 +232,10 @@ func StaticDir(d string) Option {
 		o.StaticDir = d
 	}
 }
+
+// RegisterCheck run func before registry service
+func RegisterCheck(fn func(context.Context) error) Option {
+	return func(o *Options) {
+		o.RegisterCheck = fn
+	}
+}