Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

client/grpc/stream.go

@@ -0,0 +1,84 @@
+package grpc
+
+import (
+	"context"
+	"io"
+	"sync"
+
+	"go-micro.dev/v5/client"
+	"google.golang.org/grpc"
+)
+
+// Implements the streamer interface.
+type grpcStream struct {
+	sync.RWMutex
+	closed   bool
+	err      error
+	stream   grpc.ClientStream
+	request  client.Request
+	response client.Response
+	context  context.Context
+	cancel   func()
+	release  func(error)
+}
+
+func (g *grpcStream) Context() context.Context {
+	return g.context
+}
+
+func (g *grpcStream) Request() client.Request {
+	return g.request
+}
+
+func (g *grpcStream) Response() client.Response {
+	return g.response
+}
+
+func (g *grpcStream) Send(msg interface{}) error {
+	if err := g.stream.SendMsg(msg); err != nil {
+		g.setError(err)
+		return err
+	}
+	return nil
+}
+
+func (g *grpcStream) Recv(msg interface{}) (err error) {
+	if err = g.stream.RecvMsg(msg); err != nil {
+		if err != io.EOF {
+			g.setError(err)
+		}
+		return err
+	}
+	return
+}
+
+func (g *grpcStream) Error() error {
+	g.RLock()
+	defer g.RUnlock()
+	return g.err
+}
+
+func (g *grpcStream) setError(e error) {
+	g.Lock()
+	g.err = e
+	g.Unlock()
+}
+
+func (g *grpcStream) CloseSend() error {
+	return g.stream.CloseSend()
+}
+
+func (g *grpcStream) Close() error {
+	g.Lock()
+	defer g.Unlock()
+
+	if g.closed {
+		return nil
+	}
+	// cancel the context
+	g.cancel()
+	g.closed = true
+	// release back to pool
+	g.release(g.err)
+	return nil
+}