You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: content_reader.go
    path of file: ./repos/docker-ce/components/cli/vendor/github.com/containerd/containerd/content/proxy
    
    the code of the file until where you have to start completion: /*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF 
    
func (ra *remoteReaderAt) ReadAt(p []byte, off int64) (n int, err error) {
	rr := &contentapi.ReadContentRequest{
		Digest: ra.digest,
		Offset: off,
		Size_:  int64(len(p)),
	}
	// we need a child context with cancel, or the eventually called
	// grpc.NewStream will leak the goroutine until the whole thing is cleared.
	// See comment at https://godoc.org/google.golang.org/grpc#ClientConn.NewStream
	childCtx, cancel := context.WithCancel(ra.ctx)
	// we MUST cancel the child context; see comment above
	defer cancel()
	rc, err := ra.client.Read(childCtx, rr)
	if err != nil {
		return 0, err
	}

	for len(p) > 0 {
		var resp *contentapi.ReadContentResponse
		// fill our buffer up until we can fill p.
		resp, err = rc.Recv()
		if err != nil {
			return n, err
		}

		copied := copy(p, resp.Data)
		n += copied
		p = p[copied:]
	}
	return n, nil
}