anchor.diff:  { stdenv, fetchurl, fetchFromGitHub, buildGoPackage, buildEnv }:
   
   let
  -  version = "5.7.1";
  +  version = "5.9.0";
   
     mattermost-server = buildGoPackage rec {
       name = "mattermost-server-${version}";
  
positive.code: 
      src = fetchurl {
        url = "https://releases.mattermost.com/${version}/mattermost-${version}-linux-amd64.tar.gz";
        sha256 = "0rxbgd3cb9m7rf0yg1vpd1af6x6bn0jilb0pfqr46dg42a70dx09";
      };
  
      installPhase = ''
  
negative.code:       owner = "mattermost";
        repo = "mattermost-server";
        rev = "v${version}";
        sha256 = "08h7n9smv6f1njazn4pl6pwkfmqxn93rzg69h6asicp9c4vad3m2";
      };
  
      goPackagePath = "github.com/mattermost/mattermost-server";
  