anchor.diff:  stdenv.mkDerivation rec {
     name = "iperf-${version}";
   
  -  src = fetchurl {
  -    name = "${name}.tar.gz";
  -    url = "https://iperf.fr/download/source/${name}-source.tar.gz";
  -    inherit multihash sha256;
  -  };
  +  src =
  +    if source ? fetchzipVersion then
  +      fetchFromGitHub {
  +        version = source.fetchzipVersion;
  +        owner = "esnet";
  +        repo = "iperf";
  +        rev = version;
  +        inherit sha256;
  +      }
  +    else
  +      fetchurl {
  +        name = "${name}.tar.gz";
  +        url = "https://iperf.fr/download/source/${name}-source.tar.gz";
  +        inherit multihash sha256;
  +      };
   
     postInstall = optionalString (channel == "3") ''
       ln -s iperf3 $out/bin/iperf
  
positive.code: { stdenv
  , fetchurl
  
  , channel
  
negative.code:       sha256 = "a5350777b191e910334d3a107b5e5219b72ffa393da4186da1e0a4552aeeded6";
      };
      "3" = {
        fetchzipVersion = 2;
        version = "3.1.5";
        sha256 = "58ab9d597ad5c2cac33b603770bd3e444beebc853034b0e5a00f7e612730b2cc";
      };
    };
  
    inherit (stdenv.lib)
      optionalString;
  
    source = sources."${channel}";
  
    inherit (source)
      version
      multihash
      sha256;
  