code: func (d *llvmSymbolizer) addrInfo(addr uint64) ([]plugin.Frame, error) {
  	d.Lock()
  	defer d.Unlock()
  
  	if err := d.rw.write(fmt.Sprintf("%s 0x%x", d.filename, addr-d.base)); err != nil {
  		return nil, err
  	}
  
  	var stack []plugin.Frame
  	for {
  		frame, end := d.readFrame()
  		if end {
  			break
  		}
  
  		if frame != (plugin.Frame{}) {
  			stack = append(stack, frame)
  		}
  	}
  
  	return stack, nil
  }
docs: // addrInfo returns the stack frame information for a specific program
  // address. It returns nil if the address could not be identified.