Resolve promises one after another (sequence)?

Question

I'm trying to upload files one by one (sequentially). Start method returning promise and I use it to upload file. Code works but I have problem with firefox (http/2) and I need to upload file after promise from previous is resolved. Does anyone know how to do this with $q?

var files = [
     //example obj
    {
        id: '123123',
        start: function () {
            // uploading file, returning promise
        }
    }
];

 files.forEach(function (file) {
     file.start().then(function (id) {
       //refresh file 
   })
 })