add params default decoder

cache.go

@@ -19,7 +19,7 @@ func newCache() *cache {
 	c := cache{
 		m:       make(map[reflect.Type]*structInfo),
 		regconv: make(map[reflect.Type]Converter),
-		tags:    []string{"form", "url", "schema"},
+		tags:    []string{"form", "url", "param", "schema"},
 	}
 	return &c
 }

schema.go

@@ -1,11 +1,13 @@
 package schema
 
 var (
-	defaultDecoder = NewDecoder() // form, url, schema.
+	defaultDecoder = NewDecoder() // form, url, param, schema.
 	// Form Decoder. The default instance for DecodeForm function.
 	Form = NewDecoder().SetAliasTag("form")
 	// Query Decoder. The default instance for DecodeQuery function.
-	Query = NewDecoder().SetAliasTag("url").IgnoreUnknownKeys(true) // allow unknown url queries.
+	Query = NewDecoder().SetAliasTag("url").IgnoreUnknownKeys(true) // allow unknown url queries
+	// Params Decoder. The default instance for DecodeParams function.
+	Params = NewDecoder().SetAliasTag("param").IgnoreUnknownKeys(true) //  and dynamic path parameters.
 )
 
 // Decode maps "values" to "ptr".
@@ -26,6 +28,12 @@ func DecodeQuery(values map[string][]string, ptr interface{}) error {
 	return Query.Decode(ptr, values)
 }
 
+// DecodeParams maps "values" to "ptr".
+// With "param" tag for fields.
+func DecodeParams(values map[string][]string, ptr interface{}) error {
+	return Params.Decode(ptr, values)
+}
+
 // IsErrPath reports whether the incoming error is type of unknown field passed,
 // which can be ignored when server allows unknown post values to be sent by the client.
 func IsErrPath(err error) bool {