Remove TravisCI badge (#503)

* Add documentation for using mux to serve a SPA

* r -> router to prevent shadowing

* Expand SPA acronym

* BrowserRouter link

* Add more comments to explain how the spaHandler.ServeHTTP method works

.circleci/config.yml

@@ -8,23 +8,35 @@ jobs:
       - image: circleci/golang:latest
     working_directory: /go/src/github.com/gorilla/mux
     steps: &steps
+      # Our build steps: we checkout the repo, fetch our deps, lint, and finally
+      # run "go test" on the package.
       - checkout
+      # Logs the version in our build logs, for posterity
       - run: go version
-      - run: go get -t -v ./...
+      - run:
+          name: "Fetch dependencies"
+          command: >
+            go get -t -v ./...
       # Only run gofmt, vet & lint against the latest Go version
-      - run: >
-          if [[ "$LATEST" = true ]]; then
-            go get -u golang.org/x/lint/golint
-            golint ./...
-          fi
-      - run: >
-          if [[ "$LATEST" = true ]]; then
-            diff -u <(echo -n) <(gofmt -d .)
-          fi
-      - run: >
-          if [[ "$LATEST" = true ]]; then
-            go vet -v .
-          fi
+      - run:
+          name: "Run golint"
+          command: >
+            if [ "${LATEST}" = true ] && [ -z "${SKIP_GOLINT}" ]; then
+              go get -u golang.org/x/lint/golint
+              golint ./...
+            fi
+      - run:
+          name: "Run gofmt"
+          command: >
+            if [[ "${LATEST}" = true ]]; then
+              diff -u <(echo -n) <(gofmt -d -e .)
+            fi
+      - run:
+          name: "Run go vet"
+          command:  >
+            if [[ "${LATEST}" = true ]]; then
+              go vet -v ./...
+            fi
       - run: go test -v -race ./...
 
   "latest":

README.md

@@ -1,7 +1,6 @@
 # gorilla/mux
 
 [![GoDoc](https://godoc.org/github.com/gorilla/mux?status.svg)](https://godoc.org/github.com/gorilla/mux)
-[![Build Status](https://travis-ci.org/gorilla/mux.svg?branch=master)](https://travis-ci.org/gorilla/mux)
 [![CircleCI](https://circleci.com/gh/gorilla/mux.svg?style=svg)](https://circleci.com/gh/gorilla/mux)
 [![Sourcegraph](https://sourcegraph.com/github.com/gorilla/mux/-/badge.svg)](https://sourcegraph.com/github.com/gorilla/mux?badge)
 
@@ -26,6 +25,7 @@ The name mux stands for "HTTP request multiplexer". Like the standard `http.Serv
 * [Examples](#examples)
 * [Matching Routes](#matching-routes)
 * [Static Files](#static-files)
+* [Serving Single Page Applications](#serving-single-page-applications) (e.g. React, Vue, Ember.js, etc.)
 * [Registered URLs](#registered-urls)
 * [Walking Routes](#walking-routes)
 * [Graceful Shutdown](#graceful-shutdown)
@@ -212,6 +212,93 @@ func main() {
 }
 ```
 
+### Serving Single Page Applications
+
+Most of the time it makes sense to serve your SPA on a separate web server from your API,
+but sometimes it's desirable to serve them both from one place. It's possible to write a simple
+handler for serving your SPA (for use with React Router's [BrowserRouter](https://reacttraining.com/react-router/web/api/BrowserRouter) for example), and leverage
+mux's powerful routing for your API endpoints.
+
+```go
+package main
+
+import (
+	"encoding/json"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/gorilla/mux"
+)
+
+// spaHandler implements the http.Handler interface, so we can use it
+// to respond to HTTP requests. The path to the static directory and
+// path to the index file within that static directory are used to
+// serve the SPA in the given static directory.
+type spaHandler struct {
+	staticPath string
+	indexPath  string
+}
+
+// ServeHTTP inspects the URL path to locate a file within the static dir
+// on the SPA handler. If a file is found, it will be served. If not, the
+// file located at the index path on the SPA handler will be served. This
+// is suitable behavior for serving an SPA (single page application).
+func (h spaHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+    // get the absolute path to prevent directory traversal
+	path, err := filepath.Abs(r.URL.Path)
+	if err != nil {
+        // if we failed to get the absolute path respond with a 400 bad request
+        // and stop
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+    // prepend the path with the path to the static directory
+	path = filepath.Join(h.staticPath, path)
+
+    // check whether a file exists at the given path
+	_, err = os.Stat(path)
+	if os.IsNotExist(err) {
+		// file does not exist, serve index.html
+		http.ServeFile(w, r, filepath.Join(h.staticPath, h.indexPath))
+		return
+	} else if err != nil {
+        // if we got an error (that wasn't that the file doesn't exist) stating the
+        // file, return a 500 internal server error and stop
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+    // otherwise, use http.FileServer to serve the static dir
+	http.FileServer(http.Dir(h.staticPath)).ServeHTTP(w, r)
+}
+
+func main() {
+	router := mux.NewRouter()
+
+	router.HandleFunc("/api/health", func(w http.ResponseWriter, r *http.Request) {
+		// an example API handler
+		json.NewEncoder(w).Encode(map[string]bool{"ok": true})
+	})
+
+	spa := spaHandler{staticPath: "build", indexPath: "index.html"}
+	router.PathPrefix("/").Handler(spa)
+
+	srv := &http.Server{
+		Handler: router,
+		Addr:    "127.0.0.1:8000",
+		// Good practice: enforce timeouts for servers you create!
+		WriteTimeout: 15 * time.Second,
+		ReadTimeout:  15 * time.Second,
+	}
+
+	log.Fatal(srv.ListenAndServe())
+}
+```
+
 ### Registered URLs
 
 Now let's see how to build registered URLs.

go.mod

@@ -1 +1,3 @@
 module github.com/gorilla/mux
+
+go 1.12

mux.go

@@ -111,10 +111,8 @@ func copyRouteConf(r routeConf) routeConf {
 		c.regexp.queries = append(c.regexp.queries, copyRouteRegexp(q))
 	}
 
-	c.matchers = make([]matcher, 0, len(r.matchers))
-	for _, m := range r.matchers {
-		c.matchers = append(c.matchers, m)
-	}
+	c.matchers = make([]matcher, len(r.matchers))
+	copy(c.matchers, r.matchers)
 
 	return c
 }

mux_test.go

@@ -1943,7 +1943,7 @@ type TestA301ResponseWriter struct {
 }
 
 func (ho *TestA301ResponseWriter) Header() http.Header {
-	return http.Header(ho.hh)
+	return ho.hh
 }
 
 func (ho *TestA301ResponseWriter) Write(b []byte) (int, error) {