code: func CompressorStrategy(near int64) MergeStrategy {
  	return func(chunks []bgzf.Chunk) []bgzf.Chunk {
  		if len(chunks) == 0 {
  			return nil
  		}
  		for c := 1; c < len(chunks); c++ {
  			leftChunk := chunks[c-1]
  			rightChunk := &chunks[c]
  			if leftChunk.End.File+near >= rightChunk.Begin.File {
  				rightChunk.Begin = leftChunk.Begin
  				if vOffset(leftChunk.End) > vOffset(rightChunk.End) {
  					rightChunk.End = leftChunk.End
  				}
  				chunks = append(chunks[:c-1], chunks[c:]...)
  				c--
  			}
  		}
  		return chunks
  	}
  }
docs: // CompressorStrategy returns a MergeStrategy that will merge bgzf.Chunks
  // that have a distance between BGZF block starts less than or equal
  // to near.