custom golang's pkg name

[sishui]

What type of PR is this?
fix: #14 ( pr #13, after rebase, recommit, and proto-gen-go using version 1.28.0)
When the file path does differ from the go_package name, the generated pb.fast.go is not available, although the official documentation does not recommend this, but it is legal.
ps:

option go_package = "github.com/cloudwego/fastpb/examples/fastpb_gen/user/player;playercustom";
What this PR does / why we need it (en: English/zh: Chinese):
en: Fix the generated file is not available when the package name and path of custom golang are different
zh: 修复自定义golang的包名与路径不同时，生成的文件不可用

[HeyJavaBean]

pr check 没过，重新提一下吧

[sishui]

@HeyJavaBean 我看了下check license header 没过，这个我要怎么弄，之前没弄过

ERROR the following files don't have a valid license header: 
benchmark/benchmark.go
benchmark/benchmark_fastpb.go
benchmark/benchmark_fastpb_test.go
benchmark/benchmark_gogo.go
benchmark/benchmark_gogo_test.go
benchmark/benchmark_golang.go
benchmark/benchmark_golang_test.go
benchmark/benchmark_test.go
examples/demo.go
fastpb.go
fastpb_impl.go
fastpb_impl_test.go
protoc-gen-fastpb/generator/generator.go
protoc-gen-fastpb/main.go
version.go
wire_test.go 
ERROR one or more files does not have a valid license header 

[HeyJavaBean]

这个 check license header 好像有点问题，先跳过吧