Introduce go chi web framework as frontend of macaron, so that we can move routes from macaron to chi step by step (#7420)

* When route cannot be found on chi, go to macaron

* Stick chi version to 1.5.0

* Follow router log setting

vendor/github.com/go-chi/chi/context.go

@@ -0,0 +1,172 @@
+package chi
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"strings"
+)
+
+// URLParam returns the url parameter from a http.Request object.
+func URLParam(r *http.Request, key string) string {
+	if rctx := RouteContext(r.Context()); rctx != nil {
+		return rctx.URLParam(key)
+	}
+	return ""
+}
+
+// URLParamFromCtx returns the url parameter from a http.Request Context.
+func URLParamFromCtx(ctx context.Context, key string) string {
+	if rctx := RouteContext(ctx); rctx != nil {
+		return rctx.URLParam(key)
+	}
+	return ""
+}
+
+// RouteContext returns chi's routing Context object from a
+// http.Request Context.
+func RouteContext(ctx context.Context) *Context {
+	val, _ := ctx.Value(RouteCtxKey).(*Context)
+	return val
+}
+
+// ServerBaseContext wraps an http.Handler to set the request context to the
+// `baseCtx`.
+func ServerBaseContext(baseCtx context.Context, h http.Handler) http.Handler {
+	fn := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		baseCtx := baseCtx
+
+		// Copy over default net/http server context keys
+		if v, ok := ctx.Value(http.ServerContextKey).(*http.Server); ok {
+			baseCtx = context.WithValue(baseCtx, http.ServerContextKey, v)
+		}
+		if v, ok := ctx.Value(http.LocalAddrContextKey).(net.Addr); ok {
+			baseCtx = context.WithValue(baseCtx, http.LocalAddrContextKey, v)
+		}
+
+		h.ServeHTTP(w, r.WithContext(baseCtx))
+	})
+	return fn
+}
+
+// NewRouteContext returns a new routing Context object.
+func NewRouteContext() *Context {
+	return &Context{}
+}
+
+var (
+	// RouteCtxKey is the context.Context key to store the request context.
+	RouteCtxKey = &contextKey{"RouteContext"}
+)
+
+// Context is the default routing context set on the root node of a
+// request context to track route patterns, URL parameters and
+// an optional routing path.
+type Context struct {
+	Routes Routes
+
+	// Routing path/method override used during the route search.
+	// See Mux#routeHTTP method.
+	RoutePath   string
+	RouteMethod string
+
+	// Routing pattern stack throughout the lifecycle of the request,
+	// across all connected routers. It is a record of all matching
+	// patterns across a stack of sub-routers.
+	RoutePatterns []string
+
+	// URLParams are the stack of routeParams captured during the
+	// routing lifecycle across a stack of sub-routers.
+	URLParams RouteParams
+
+	// The endpoint routing pattern that matched the request URI path
+	// or `RoutePath` of the current sub-router. This value will update
+	// during the lifecycle of a request passing through a stack of
+	// sub-routers.
+	routePattern string
+
+	// Route parameters matched for the current sub-router. It is
+	// intentionally unexported so it cant be tampered.
+	routeParams RouteParams
+
+	// methodNotAllowed hint
+	methodNotAllowed bool
+}
+
+// Reset a routing context to its initial state.
+func (x *Context) Reset() {
+	x.Routes = nil
+	x.RoutePath = ""
+	x.RouteMethod = ""
+	x.RoutePatterns = x.RoutePatterns[:0]
+	x.URLParams.Keys = x.URLParams.Keys[:0]
+	x.URLParams.Values = x.URLParams.Values[:0]
+
+	x.routePattern = ""
+	x.routeParams.Keys = x.routeParams.Keys[:0]
+	x.routeParams.Values = x.routeParams.Values[:0]
+	x.methodNotAllowed = false
+}
+
+// URLParam returns the corresponding URL parameter value from the request
+// routing context.
+func (x *Context) URLParam(key string) string {
+	for k := len(x.URLParams.Keys) - 1; k >= 0; k-- {
+		if x.URLParams.Keys[k] == key {
+			return x.URLParams.Values[k]
+		}
+	}
+	return ""
+}
+
+// RoutePattern builds the routing pattern string for the particular
+// request, at the particular point during routing. This means, the value
+// will change throughout the execution of a request in a router. That is
+// why its advised to only use this value after calling the next handler.
+//
+// For example,
+//
+//   func Instrument(next http.Handler) http.Handler {
+//     return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+//       next.ServeHTTP(w, r)
+//       routePattern := chi.RouteContext(r.Context()).RoutePattern()
+//       measure(w, r, routePattern)
+//   	 })
+//   }
+func (x *Context) RoutePattern() string {
+	routePattern := strings.Join(x.RoutePatterns, "")
+	return replaceWildcards(routePattern)
+}
+
+// replaceWildcards takes a route pattern and recursively replaces all
+// occurrences of "/*/" to "/".
+func replaceWildcards(p string) string {
+	if strings.Contains(p, "/*/") {
+		return replaceWildcards(strings.Replace(p, "/*/", "/", -1))
+	}
+
+	return p
+}
+
+// RouteParams is a structure to track URL routing parameters efficiently.
+type RouteParams struct {
+	Keys, Values []string
+}
+
+// Add will append a URL parameter to the end of the route param
+func (s *RouteParams) Add(key, value string) {
+	s.Keys = append(s.Keys, key)
+	s.Values = append(s.Values, value)
+}
+
+// contextKey is a value for use with context.WithValue. It's used as
+// a pointer so it fits in an interface{} without allocation. This technique
+// for defining context keys was copied from Go 1.7's new use of context in net/http.
+type contextKey struct {
+	name string
+}
+
+func (k *contextKey) String() string {
+	return "chi context value " + k.name
+}