实现：grpc内部代码实现！

recvCompress: req.Header.Get(“grpc-encoding”),
headerFields = append(headerFields, hpack.HeaderField{Name: “grpc-encoding”, Value: s.sendCompress})

stream 内有：
recvCompress string
sendCompress string

使用：

res, err := c.UnaryEcho(ctx, &pb.EchoRequest{Message: msg}, grpc.UseCompressor(gzip.Name))
!

grpc 代码实现；

  1.     if rc := stream.RecvCompress(); s.opts.dc != nil && s.opts.dc.Type() == rc {
  2.         dc = s.opts.dc
  3.     } else if rc != "" && rc != encoding.Identity {
  4.         decomp = encoding.GetCompressor(rc)
  5.         if decomp == nil {
  6.             st := status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", rc)
  7.             t.WriteStatus(stream, st)
  8.             return st.Err()
  9.         }
  10.     }
  12.     // If cp is set, use it.  Otherwise, attempt to compress the response using
  13.     // the incoming message compression method.
  14.     //
  15.     // NOTE: this needs to be ahead of all handling, https://github.com/grpc/grpc-go/issues/686.
  16.     if s.opts.cp != nil {
  17.         cp = s.opts.cp
  18.         stream.SetSendCompress(cp.Type())
  19.     } else if rc := stream.RecvCompress(); rc != "" && rc != encoding.Identity {
  20.         // Legacy compressor not specified; attempt to respond with same encoding.
  21.         comp = encoding.GetCompressor(rc)
  22.         if comp != nil {
  23.             stream.SetSendCompress(rc)
  24.         }
  25.     }