Fixes to recent extension changes. (#568)

* Fixes to recent extension changes.

* Fixes issue where gin will continue calling the handler even if next() isn't called.

* Updated docs.

api/server/extensions.go

@@ -1,7 +1,6 @@
 package server
 
 import (
-	"fmt"
 	"log"
 
 	"github.com/fnproject/fn/fnext"
@@ -10,15 +9,15 @@ import (
 // TODO: Move this into `github.com/fnproject/fn` package after main is moved out of root dir.
 var extensions = map[string]fnext.Extension{}
 
-// RegisterExtension registers the extension so it's available, but does not initialize it or anything
+// RegisterExtension registers the extension so it's available, but does not initialize it.
+// This is generally what third party extensions will use in their init() method.
 func RegisterExtension(ext fnext.Extension) {
 	extensions[ext.Name()] = ext
 }
 
-// AddExtensionByName This essentially just makes sure the extensions are ordered properly.
-// It could do some initialization if required too.
+// AddExtensionByName This essentially just makes sure the extensions are ordered properly and is
+// what the CLI uses for the `fn build-server` command. Probably not used by much else.
 func (s *Server) AddExtensionByName(name string) {
-	fmt.Printf("extensions: %+v\n", extensions)
 	e, ok := extensions[name]
 	if !ok {
 		log.Fatalf("Extension %v not registered.\n", name)
@@ -28,3 +27,10 @@ func (s *Server) AddExtensionByName(name string) {
 		log.Fatalf("Failed to add extension %v: %v\n", name, err)
 	}
 }
+
+// AddExtension both registers an extension and adds it. This is useful during extension development
+// or if you want to build a custom server without using `fn build-server`.
+func (s *Server) AddExtension(ext fnext.Extension) {
+	RegisterExtension(ext)
+	s.AddExtensionByName(ext.Name())
+}