code: func lambdaWalker(lambda func(string) error, ext string) filepath.WalkFunc {
  	walk := func(path string, f os.FileInfo, err error) error {
  		// if error occurs during traversal to path, exit and crash
  		if err != nil {
  			return err
  		}
  		// skip anything that is a directory
  		if f.IsDir() {
  			return nil
  		}
  
  		if filepath.Ext(path) == ext {
  			return lambda(path)
  		}
  
  		// ignore anything else
  		return nil
  	}
  	return walk
  }
docs: // lambdaWalker returns a walkfunc that applies lambda to every file with extension ext. Ignores all other file types.
  // Lambda should take the file path as its parameter.