code: func (h *ResponseHeader) SetBytesK(key []byte, value string) {
  	h.bufKV.value = append(h.bufKV.value[:0], value...)
  	h.SetBytesKV(key, h.bufKV.value)
  }
docs: // SetBytesK sets the given 'key: value' header.
  //
  // Use AddBytesK for setting multiple header values under the same key.