I have just published a small package for the excellent Go programming language: The new package, trace, implements a simple tracing framework. Code using this framework can emit diagnostic messages using the trace.T() function. In normal operation, calls to trace.T() have no effect and are very fast. When tracing is enabled (in order to track down a problem or to explore the inner workings of a program), listeners can record/display the trace messages.
Details can be found on the trace package home page. Comments are very welcome!