I'm encoding an image with swift using

let base64String = data!.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(rawValue: 0))

/9j/4AAQSkZJRgABAQAASABIAAD/4QBYRXhpZgAATU0AKgAAAAgAAgESAAMAAAABAAEAAIdpAAQAAAABAAAAJgAAAAAAA6ABAAMAAAABAAEAAKACAAQAAAABAAABLKADAAQAAAABAAABLAAAAAD/7QA4UGhvdG9zaG9wIDMuMAA4QklNBAQAAAAAAAA4QklNBCUAAAAAABDUHYzZjwCyBOmACZjs+EJ...

I encoded the same image with golang using

sEnc := base64.StdEncoding.EncodeToString(imageData)

/9j/2wCEAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDIBCQkJDAsMGA0NGDIhHCEyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMv/AABEIASwBLAMBIgACEQEDEQH/xAGiAAABBQEBAQEB...

When I decode the image in swift using 

let decodedData = NSData(base64EncodedString: base64String, options: NSDataBase64DecodingOptions(rawValue: 0))
var decodedimage = UIImage(data: decodedData!)

the image looks exactly the same.

When I decode swift generated base64 string in golang with

dec, err := base64.StdEncoding.DecodeString(imageData)

illegal base64 data at input byte 220+

Why are the encoded strings different? How can I fix it?

EDIT: 

eqvr h/9k=cvdR//2Q==

EDIT2:

ioutil for reading file
b, err := ioutil.ReadFile(fileName)

EDIT3: