anchor.diff:        owner = "mattermost";
         repo = "mattermost-server";
         rev = "v${version}";
  -      sha256 = "1bh53h0bmpc1qmnbpsmwkfrvj66z18m7b1xg7pqikid57ssqxjx9";
  +      sha256 = "002mbpgsk988pfjla84ngixq4jmgjgr3gj3h874y1njgz8xq0d92";
       };
   
       goPackagePath = "github.com/mattermost/mattermost-server";
  
positive.code: { stdenv, fetchurl, fetchFromGitHub, buildGoPackage, buildEnv }:
  
  let
    version = "5.15.0";
  
    mattermost-server = buildGoPackage rec {
      pname = "mattermost-server";
  
negative.code: 
      src = fetchurl {
        url = "https://releases.mattermost.com/${version}/mattermost-${version}-linux-amd64.tar.gz";
        sha256 = "08sp4idms7qyafk59plfzk380r72bphqa3ka648v25wh5h3293pn";
      };
  
      installPhase = ''
  