the other way of reading last line

gistfile1.txt

func readLastLine(f *os.File) (string, error) {                                                                                                                                              
  sz, err := f.Seek(0, io.SeekEnd)                                                                                                                                                           
  if err != nil {                                                                                                                                                                            
    return "", err                                                                                                                                                                           
  }                                                                                                                                                                                          
  // ensure we avoid eventually last \n                                                                                                                                                      
  deep := sz - int64(len("\n")+1)                                                                                                                                                            
  buf := make([]byte, 1)                                                                                                                                                                     
  // moon walk one byte at time                                                                                                                                                              
  for {                                                                                                                                                                                      
    _, err := f.ReadAt(buf, deep)                                                                                                                                                            
    if err != nil {                                                                                                                                                                          
      return "", err                                                                                                                                                                         
    }                                                                                                                                                                                        
    // find newline position from above                                                                                                                                                      
    if string(buf) == "\n" {                                                                                                                                                                 
      // we dont need newline above                                                                                                                                                          
      deep = deep + int64(len("\n"))                                                                                                                                                         
      break                                                                                                                                                                                  
    }                                                                                                                                                                                        
    deep--                                                                                                                                                                                   
  }                                                                                                                                                                                          
  b := make([]byte, sz-deep)                                                                                                                                                                 
  num, err := f.ReadAt(b, deep)                                                                                                                                                              
  fmt.Printf("deep %d\n", deep)                                                                                                                                                              
  b = b[:num]                                                                                                                                                                                
  return string(b), nil                                                                                                                                                                      
}