protobuf: Why i can not upgrade to version 3? Help me ~~

protoc --version libprotoc 3.4.0 and has been running: go get -u github.com/golang/protobuf/protoc-gen-go it means protoc version is 3.4.0 and protoc-gen-go is latest version and also had already added syntax = "proto3"; at a.proto file head when i run protoc --go_out=. a.proto the Code generated by protoc-gen-go also contains // This is a compile-time assertion to ensure that this generated file // is compatible with the proto package it is being compiled against. // A compilation error at this line likely means your copy of the // proto package needs to be updated. and var fileDescriptor0 = []byte{ // 120 bytes of a gzipped FileDescriptorProto 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x12, 0x29, 0x33, 0xd4, 0x4f, 0xcd, 0x2b, 0xc9, 0x2c, 0xa9, 0xd4, 0x4f, 0x4a, 0xcc, 0xc9, 0xd1, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0xe2, 0x2c, 0x33, 0xd4, 0x83, 0x88, 0x2a, 0x45, 0x71, 0xb1, 0x38, 0x25, 0xe6, 0xe4, 0x08, 0xc9, 0x72, 0x71, 0x15, 0xe4, 0x17, 0x67, 0x96, 0x64, 0xe6, 0xe7, 0xc5, 0x57, 0x48, 0x30, 0x2a, 0x30, 0x6a, 0x30, 0x05, 0x71, 0xc2, 0x44, 0x22, 0x50, 0xa4, 0x2b, 0x25, 0x98, 0x50, 0xa5, 0x23, 0x85, 0x44, 0xb8, 0x58, 0x13, 0xf3, 0xd2, 0x73, 0x52, 0x25, 0x98, 0xc1, 0x32, 0x10, 0x8e, 0x13, 0xcf, 0x2a, 0x26, 0x84, 0x4d, 0x49, 0x6c, 0x60, 0xbb, 0x8d, 0x01, 0x01, 0x00, 0x00, 0xff, 0xff, 0x01, 0x63, 0xdb, 0x39, 0x93, 0x00, 0x00, 0x00, }