go/src/runtime/trace/trace.go

// Start enables tracing for the current program.
// While tracing, the trace will be buffered and written to w.
// Start returns an error if tracing is already enabled.
func Start(w io.Writer) error { … }

// Stop stops the current tracing, if any.
// Stop only returns after all the writes for the trace have completed.
func Stop() { … }

var tracing …