code: func (h *RequestHeader) SetBytesV(key string, value []byte) {
  	k := getHeaderKeyBytes(&h.bufKV, key, h.disableNormalizing)
  	h.SetCanonical(k, value)
  }
docs: // SetBytesV sets the given 'key: value' header.
  //
  // Use AddBytesV for setting multiple header values under the same key.