add an edge case from httprouter (#1407)

path.go

@@ -41,7 +41,7 @@ func cleanPath(p string) string {
 		buf[0] = '/'
 	}
 
-	trailing := n > 2 && p[n-1] == '/'
+	trailing := n > 1 && p[n-1] == '/'
 
 	// A bit more clunky without a 'lazybuf' like the path package, but the loop
 	// gets completely inlined (bufApp). So in contrast to the path package this

path_test.go

@@ -24,6 +24,7 @@ var cleanTests = []struct {
 
 	// missing root
 	{"", "/"},
+	{"a/", "/a/"},
 	{"abc", "/abc"},
 	{"abc/def", "/abc/def"},
 	{"a/b/c", "/a/b/c"},