fix errcheck warnings (#1739)

render/text.go

@@ -20,8 +20,7 @@ var plainContentType = []string{"text/plain; charset=utf-8"}
 
 // Render (String) writes data with custom ContentType.
 func (r String) Render(w http.ResponseWriter) error {
-	WriteString(w, r.Format, r.Data)
-	return nil
+	return WriteString(w, r.Format, r.Data)
 }
 
 // WriteContentType (String) writes Plain ContentType.
@@ -30,11 +29,12 @@ func (r String) WriteContentType(w http.ResponseWriter) {
 }
 
 // WriteString writes data according to its format and write custom ContentType.
-func WriteString(w http.ResponseWriter, format string, data []interface{}) {
+func WriteString(w http.ResponseWriter, format string, data []interface{}) (err error) {
 	writeContentType(w, plainContentType)
 	if len(data) > 0 {
-		fmt.Fprintf(w, format, data...)
+		_, err = fmt.Fprintf(w, format, data...)
 		return
 	}
-	io.WriteString(w, format)
+	_, err = io.WriteString(w, format)
+	return
 }