The readme uses history so surely the author knows this?

    function preexec_go() {
      local command_line=$(history 1 | sed 's/^ *[0-9]* *//')
      if [[ -n "$command_line" && "$command_line" != "preexec_go" ]]; then
        # CHANGE THIS PATH to the location of your 'envoy' executable
        ( 
    ~/Desktop/projects/envoy/envoy "$command_line" >/dev/null 2>&1 & ) disown
      fi
    }
    trap 'preexec_go' DEBUG