cmd/protoc-gen-go-grpc: fix method name in interceptor info (#3889)

diff --git a/cmd/protoc-gen-go-grpc/grpc.go b/cmd/protoc-gen-go-grpc/grpc.go
index 919b5d4..efc92ac 100644
--- a/cmd/protoc-gen-go-grpc/grpc.go
+++ b/cmd/protoc-gen-go-grpc/grpc.go
@@ -351,7 +351,7 @@
 		g.P("if interceptor == nil { return srv.(", service.GoName, "Server).", method.GoName, "(ctx, in) }")
 		g.P("info := &", grpcPackage.Ident("UnaryServerInfo"), "{")
 		g.P("Server: srv,")
-		g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", service.Desc.FullName(), method.GoName)), ",")
+		g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", service.Desc.FullName(), method.Desc.Name())), ",")
 		g.P("}")
 		g.P("handler := func(ctx ", contextPackage.Ident("Context"), ", req interface{}) (interface{}, error) {")
 		g.P("return srv.(", service.GoName, "Server).", method.GoName, "(ctx, req.(*", method.Input.GoIdent, "))")