Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

client/grpc/options.go

@@ -0,0 +1,143 @@
+// Package grpc provides a gRPC options
+package grpc
+
+import (
+	"context"
+	"crypto/tls"
+
+	"go-micro.dev/v5/client"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/encoding"
+)
+
+var (
+	// DefaultPoolMaxStreams maximum streams on a connectioin
+	// (20).
+	DefaultPoolMaxStreams = 20
+
+	// DefaultPoolMaxIdle maximum idle conns of a pool
+	// (50).
+	DefaultPoolMaxIdle = 50
+
+	// DefaultMaxRecvMsgSize maximum message that client can receive
+	// (4 MB).
+	DefaultMaxRecvMsgSize = 1024 * 1024 * 4
+
+	// DefaultMaxSendMsgSize maximum message that client can send
+	// (4 MB).
+	DefaultMaxSendMsgSize = 1024 * 1024 * 4
+)
+
+type poolMaxStreams struct{}
+type poolMaxIdle struct{}
+type codecsKey struct{}
+type tlsAuth struct{}
+type maxRecvMsgSizeKey struct{}
+type maxSendMsgSizeKey struct{}
+type grpcDialOptions struct{}
+type grpcCallOptions struct{}
+
+// maximum streams on a connectioin.
+func PoolMaxStreams(n int) client.Option {
+	return func(o *client.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, poolMaxStreams{}, n)
+	}
+}
+
+// maximum idle conns of a pool.
+func PoolMaxIdle(d int) client.Option {
+	return func(o *client.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, poolMaxIdle{}, d)
+	}
+}
+
+// gRPC Codec to be used to encode/decode requests for a given content type.
+func Codec(contentType string, c encoding.Codec) client.Option {
+	return func(o *client.Options) {
+		codecs := make(map[string]encoding.Codec)
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		if v := o.Context.Value(codecsKey{}); v != nil {
+			codecs = v.(map[string]encoding.Codec)
+		}
+		codecs[contentType] = c
+		o.Context = context.WithValue(o.Context, codecsKey{}, codecs)
+	}
+}
+
+// AuthTLS should be used to setup a secure authentication using TLS.
+func AuthTLS(t *tls.Config) client.Option {
+	return func(o *client.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, tlsAuth{}, t)
+	}
+}
+
+// MaxRecvMsgSize set the maximum size of message that client can receive.
+func MaxRecvMsgSize(s int) client.Option {
+	return func(o *client.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, maxRecvMsgSizeKey{}, s)
+	}
+}
+
+// MaxSendMsgSize set the maximum size of message that client can send.
+func MaxSendMsgSize(s int) client.Option {
+	return func(o *client.Options) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, maxSendMsgSizeKey{}, s)
+	}
+}
+
+// DialOptions to be used to configure gRPC dial options.
+func DialOptions(opts ...grpc.DialOption) client.CallOption {
+	return func(o *client.CallOptions) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, grpcDialOptions{}, opts)
+	}
+}
+
+// CallOptions to be used to configure gRPC call options.
+func CallOptions(opts ...grpc.CallOption) client.CallOption {
+	return func(o *client.CallOptions) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, grpcCallOptions{}, opts)
+	}
+}
+
+func callOpts(opts client.CallOptions) []grpc.CallOption {
+	if opts.Context == nil {
+		return nil
+	}
+
+	v := opts.Context.Value(grpcCallOptions{})
+
+	if v == nil {
+		return nil
+	}
+
+	options, ok := v.([]grpc.CallOption)
+
+	if !ok {
+		return nil
+	}
+
+	return options
+}