fix #1838 (#1839)

rest/httpc/vars.go

@@ -10,7 +10,7 @@ const (
 	slash           = "/"
 	colon           = ':'
 	contentType     = "Content-Type"
-	applicationJson = "application/json"
+	applicationJson = "application/json; charset=utf-8"
 )
 
 // ErrGetWithBody indicates that GET request with body.

rest/httpx/vars.go

@@ -2,7 +2,7 @@ package httpx
 
 const (
 	// ApplicationJson means application/json.
-	ApplicationJson = "application/json"
+	ApplicationJson = "application/json; charset=utf-8"
 	// ContentEncoding means Content-Encoding.
 	ContentEncoding = "Content-Encoding"
 	// ContentSecurity means X-Content-Security.