title: Golang dynamic sizing slice when reading a file using buffo.read
body: <p>I have a problem where, I need to use bufio.read to read a tsv file line by line and I need to record how many bytes each line Ive read is. </p>
  
  <p>The problem is, It seems like I can't just initialize an empty slice and pass it into bufio.read and expect the slice to contain the entire line of the file. </p>
  
  <pre><code>file, _ := os.Open("file.tsv")
  
  reader := bufio.NewReader(file)
  
  b := make([]byte, 10)
  for {
      bytesRead, err:= reader.Read(b)
      fmt.Println(bytesRead, b)
      if err != nil {
          break
      }
  }
  </code></pre>
  
  <p>So, for this example, since I specified the slice to be 10 bytes, the reader will read at most 10 bytes even if the line is bigger than 10 bytes.</p>
  
  <p>However:</p>
  
  <pre><code>file, _ := os.Open("file.tsv")
  
  reader := bufio.NewReader(file)
  
  b := byte{} //or var b []byte
  for {
      bytesRead, err:= reader.Read(b)
      fmt.Println(bytesRead, b)
      if err != nil {
          break
      }
  }
  </code></pre>
  
  <p>This will always read 0 bytes and I assume its because the buffer is length 0 or capacity 0. </p>
  
  <p>How do I read a file Line by line, save the entire line in a variable or buffer, and return exactly how many bytes Ive read?</p>
  
  <p>Thanks!</p>