code: func (b *base) appendRemainingLength() {
  	// Calculate and encode the Remaining Length.
  	rl := encodeLength(uint32(len(b.variableHeader) + len(b.payload)))
  
  	// Append the Remaining Length to the fixed header.
  	b.fixedHeader = appendRemainingLength(b.fixedHeader, rl)
  }
docs: // appendRemainingLength appends the Remaining Length
  // to the fixed header.