title: Split string based on byte length in golang
body: <p>The http request header has a 4k length limit.
  I want to split the string which I want to include in the header based on this limit.
  Should I use <code>[]byte(str)</code> to split first then convert back to string using <code>string([]byte)</code> for each split part? 
  Is there any simpler way to do it?</p>