Link to godoc in type-check error messages

This beats trying to enumerate the accepted types by hand.

web/middleware.go

@@ -50,6 +50,8 @@ func (s *cStack) ServeHTTPC(c C, w http.ResponseWriter, r *http.Request) {
 	s.m.ServeHTTP(w, r)
 }
 
+const unknownMiddleware = `Unknown middleware type %T. See http://godoc.org/github.com/zenazn/goji/web#MiddlewareType for a list of acceptable types.`
+
 func (m *mStack) appendLayer(fn interface{}) {
 	ml := mLayer{orig: fn}
 	switch f := fn.(type) {
@@ -60,9 +62,7 @@ func (m *mStack) appendLayer(fn interface{}) {
 	case func(*C, http.Handler) http.Handler:
 		ml.fn = f
 	default:
-		log.Fatalf(`Unknown middleware type %v. Expected a function `+
-			`with signature "func(http.Handler) http.Handler" or `+
-			`"func(*web.C, http.Handler) http.Handler".`, fn)
+		log.Fatalf(unknownMiddleware, fn)
 	}
 	m.stack = append(m.stack, ml)
 }

web/pattern.go

@@ -31,6 +31,8 @@ type Pattern interface {
 	Run(r *http.Request, c *C)
 }
 
+const unknownPattern = `Unknown pattern type %T. See http://godoc.org/github.com/zenazn/goji/web#PatternType for a list of acceptable types.`
+
 /*
 ParsePattern is used internally by Goji to parse route patterns. It is exposed
 publicly to make it easier to write thin wrappers around the built-in Pattern
@@ -50,8 +52,7 @@ func ParsePattern(raw PatternType) Pattern {
 	case string:
 		return parseStringPattern(v)
 	default:
-		log.Fatalf("Unknown pattern type %T. Expected a web.Pattern, "+
-			"regexp.Regexp, or a string.", v)
+		log.Fatalf(unknownPattern, v)
+		panic("log.Fatalf does not return")
 	}
-	panic("log.Fatalf does not return")
 }

web/router.go

@@ -66,6 +66,8 @@ func (h netHTTPWrap) ServeHTTPC(c C, w http.ResponseWriter, r *http.Request) {
 	h.Handler.ServeHTTP(w, r)
 }
 
+const unknownHandler = `Unknown handler type %T. See http://godoc.org/github.com/zenazn/goji/web#HandlerType for a list of acceptable types.`
+
 func parseHandler(h interface{}) Handler {
 	switch f := h.(type) {
 	case Handler:
@@ -77,12 +79,9 @@ func parseHandler(h interface{}) Handler {
 	case func(w http.ResponseWriter, r *http.Request):
 		return netHTTPWrap{http.HandlerFunc(f)}
 	default:
-		log.Fatalf("Unknown handler type %v. Expected a web.Handler, "+
-			"a http.Handler, or a function with signature func(C, "+
-			"http.ResponseWriter, *http.Request) or "+
-			"func(http.ResponseWriter, *http.Request)", h)
+		log.Fatalf(unknownHandler, h)
+		panic("log.Fatalf does not return")
 	}
-	panic("log.Fatalf does not return")
 }
 
 func httpMethod(mname string) method {