package main 
 
import( 
  "fmt" 
  "os" 
  "flag" 
  "io" 
  "io/ioutil" 
  "bufio" 
  "time" 
) 
 
func read1(path string)string{ 
  fi,err := os.Open(path) 
  if err != nil{ 
    panic(err) 
  } 
  defer fi.Close() 
 
  chunks := make([]byte,1024,1024) 
  buf := make([]byte,1024) 
  for{ 
    n,err := fi.Read(buf) 
    if err != nil  err != io.EOF{panic(err)} 
    if 0 ==n {break} 
    chunks=append(chunks,buf[:n]...) 
    // fmt.Println(string(buf[:n])) 
  } 
  return string(chunks) 
} 
 
func read2(path string)string{ 
  fi,err := os.Open(path) 
  if err != nil{panic(err)} 
  defer fi.Close() 
  r := bufio.NewReader(fi) 
   
  chunks := make([]byte,1024,1024) 
    
  buf := make([]byte,1024) 
  for{ 
    n,err := r.Read(buf) 
    if err != nil  err != io.EOF{panic(err)} 
    if 0 ==n {break} 
    chunks=append(chunks,buf[:n]...) 
    // fmt.Println(string(buf[:n])) 
  } 
  return string(chunks) 
} 
 
func read3(path string)string{ 
  fi,err := os.Open(path) 
  if err != nil{panic(err)} 
  defer fi.Close() 
  fd,err := ioutil.ReadAll(fi) 
  // fmt.Println(string(fd)) 
  return string(fd) 
} 
 
func main(){ 
   
  flag.Parse() 
  file := flag.Arg(0) 
  f,err := ioutil.ReadFile(file) 
  if err != nil{ 
    fmt.Printf("%s\n",err) 
    panic(err) 
  } 
  fmt.Println(string(f)) 
  start := time.Now() 
  read1(file) 
  t1 := time.Now() 
  fmt.Printf("Cost time %v\n",t1.Sub(start)) 
  read2(file) 
  t2 := time.Now() 
  fmt.Printf("Cost time %v\n",t2.Sub(t1)) 
  read3(file) 
  t3 := time.Now() 
  fmt.Printf("Cost time %v\n",t3.Sub(t2)) 
 
} 

Cost time 105.006ms 
Cost time 68.0039ms 
Cost time 31.0018ms 

Cost time 390.0223ms 
Cost time 194.0111ms 
Cost time 83.0048ms 

Cost time 40.8043338s 
Cost time 1m5.0407201s 
Cost time 8.8155043s