code: public static <T> T withWriterAppend(Path self, @ClosureParams(value = SimpleType.class, options = "java.io.Writer") Closure<T> closure) throws IOException {
          return withWriterAppend(self, Charset.defaultCharset().name(), closure);
      }
docs: Create a new BufferedWriter for this file in append mode.  The writer
  is passed to the closure and is closed after the closure returns.
  The writer will not write a BOM.
  
  @param self    a Path
  @param closure a closure
  @return the value returned by the closure
  @throws java.io.IOException if an IOException occurs.
  @since 2.3.0