code: func (req *Request) MayContinue() bool {
  	return bytes.Equal(req.Header.peek(strExpect), str100Continue)
  }
docs: // MayContinue returns true if the request contains
  // 'Expect: 100-continue' header.
  //
  // The caller must do one of the following actions if MayContinue returns true:
  //
  //     - Either send StatusExpectationFailed response if request headers don't
  //       satisfy the caller.
  //     - Or send StatusContinue response before reading request body
  //       with ContinueReadBody.
  //     - Or close the connection.