code: func ReadAll(reader io.Reader) ([]string, error) {
  	if reader == nil {
  		return nil, nil
  	}
  
  	scanner := bufio.NewScanner(reader)
  	var excludes []string
  	currentLine := 0
  
  	utf8bom := []byte{0xEF, 0xBB, 0xBF}
  	for scanner.Scan() {
  		scannedBytes := scanner.Bytes()
  		// We trim UTF8 BOM
  		if currentLine == 0 {
  			scannedBytes = bytes.TrimPrefix(scannedBytes, utf8bom)
  		}
  		pattern := string(scannedBytes)
  		currentLine++
  		// Lines starting with # (comments) are ignored before processing
  		if strings.HasPrefix(pattern, "#") {
  			continue
  		}
  		pattern = strings.TrimSpace(pattern)
  		if pattern == "" {
  			continue
  		}
  		// normalize absolute paths to paths relative to the context
  		// (taking care of '!' prefix)
  		invert := pattern[0] == '!'
  		if invert {
  			pattern = strings.TrimSpace(pattern[1:])
  		}
  		if len(pattern) > 0 {
  			pattern = filepath.Clean(pattern)
  			pattern = filepath.ToSlash(pattern)
  			if len(pattern) > 1 && pattern[0] == '/' {
  				pattern = pattern[1:]
  			}
  		}
  		if invert {
  			pattern = "!" + pattern
  		}
  
  		excludes = append(excludes, pattern)
  	}
  	if err := scanner.Err(); err != nil {
  		return nil, fmt.Errorf("Error reading .dockerignore: %v", err)
  	}
  	return excludes, nil
  }
docs: // ReadAll reads a .dockerignore file and returns the list of file patterns
  // to ignore. Note this will trim whitespace from each line as well
  // as use GO's "clean" func to get the shortest/cleanest path for each.