templateform.RenderForm now renders textarea

When RenderForm encounters a field with the structTag `form` value
type `textarea` it renders an actual <textarea> html tag.

@@ -327,7 +327,6 @@ func ParseForm(form url.Values, obj interface{}) error {
 	return nil
 }
 
-
 var unKind = map[reflect.Kind]bool{
 	reflect.Uintptr:       true,
 	reflect.Complex64:     true,
@@ -367,12 +366,30 @@ func RenderForm(obj interface{}) template.HTML {
       continue
     }
 
-		raw = append(raw, fmt.Sprintf(`%v<input name="%v" type="%v" value="%v">`,
-			label, name, fType, fieldV.Interface()))
+		raw = append(raw, renderFormField(label, name, fType, fieldV.Interface()))
 	}
 	return template.HTML(strings.Join(raw, "</br>"))
 }
 
+func renderFormField(label, name, fType string, value interface{}) string {
+  if isValidForInput(fType) {
+    return fmt.Sprintf(`%v<input name="%v" type="%v" value="%v">`, label, name, fType, value)
+  }
+
+  return fmt.Sprintf(`%v<%v name="%v">%v</%v>`, label, fType, name, value, fType)
+}
+
+func isValidForInput(fType string) bool {
+  validInputTypes := strings.Fields("text password checkbox radio submit reset hidden image file button")
+  for _, validType := range validInputTypes {
+    if fType == validType {
+      return true
+    }
+  }
+  return false
+}
+
+
 // parseFormTag takes the stuct-tag of a StructField and parses the `form` value.
 // returned are the form label, name-property, type and wether the field should be ignored.
 func parseFormTag(fieldT reflect.StructField) (label, name, fType string, ignored bool) {

@@ -148,9 +148,10 @@ func TestRenderForm(t *testing.T) {
 		Sex   string
 		Email []string
 		Intro string `form:",textarea"`
+		Ignored string `form:"-"`
 	}
 
-	u := user{Name: "test"}
+  u := user{Name: "test", Intro: "Some Text"}
 	output := RenderForm(u)
 	if output != template.HTML("") {
 		t.Errorf("output should be empty but got %v", output)
@@ -160,12 +161,24 @@ func TestRenderForm(t *testing.T) {
 		`Name: <input name="username" type="text" value="test"></br>` +
 			`年龄：<input name="age" type="text" value="0"></br>` +
 			`Sex: <input name="Sex" type="text" value=""></br>` +
-			`Intro: <input name="Intro" type="textarea" value="">`)
+			`Intro: <textarea name="Intro">Some Text</textarea>`)
 	if output != result {
 		t.Errorf("output should equal `%v` but got `%v`", result, output)
 	}
 }
 
+func TestRenderFormField(t *testing.T) {
+  html := renderFormField("Label: ", "Name", "text", "Value")
+  if html != `Label: <input name="Name" type="text" value="Value">` {
+    t.Errorf("Wrong html output for input[type=text]: %v ", html)
+  }
+
+  html = renderFormField("Label: ", "Name", "textarea", "Value")
+  if html != `Label: <textarea name="Name">Value</textarea>` {
+    t.Errorf("Wrong html output for textarea: %v ", html)
+  }
+}
+
 func TestParseFormTag(t *testing.T) {
   // create struct to contain field with different types of struct-tag `form`
 	type user struct {