Solving protoc-gen-go: unable to determine Go import path problem by adding a "M" argument

Same symptom as https://stackoverflow.com/questions/70586511/protoc-gen-go-unable-to-determine-go-import-path-for-simple-proto

> For simple proto file with following content.
>
> syntax="proto3";
>
> package main;
>
> message Person {
> string name = 1;
> int32 age = 2;
> }
>
> I am trying to generate go code for it using protoc. I run:
>
> protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative simple.proto
>
> I receive following error:
>
> protoc-gen-go: unable to determine Go import path for "simple.proto"
>
> Please specify either:
> • a "go_package" option in the .proto source file, or
> • a "M" argument on the command line.

All the answer there focus on the first option -- adding a "go_package" option in the .proto source file, but I'm looking for the answer for the second option "a "M" argument on the command line".

Same as the comments under https://stackoverflow.com/a/62540631/2125837

I'm looking for ways to change the module path via protoc, to generate Go code for both a client and server that are part of different modules, I tried using go_opt=module but it doesn't work with source_relative.

Is there any ways to make it work by adding "a "M" argument on the command line", instead of adding a "go_package" option in the .proto source file please?

Specifically, for the file of
https://github.com/mmcc007/go/blob/master/examples/helloworld/helloworld/helloworld.proto

Here are my failed attempts:

$ protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative --proto_path=examples/helloworld/helloworld helloworld.proto 

protoc-gen-go: unable to determine Go import path for "helloworld.proto"
. . .
--go_out: protoc-gen-go: Plugin failed with status code 1.


$ protoc --go_out=. --go_opt=paths=source_relative --go-grpc_out=. --go-grpc_opt=paths=source_relative --proto_path=examples/helloworld/helloworld --go_opt=Mhelloworld.proto=github.com/mmcc007/go/blob/master/examples/helloworld/helloworld helloworld.proto 

protoc-gen-go-grpc: unable to determine Go import path for "helloworld.proto"
. . .
--go_out: protoc-gen-go: Plugin failed with status code 1.

I found this to be working using --proto_path for easy reference using "THE M FLAG"

protoc --proto_path=./proto \
  --go_out=./go \
  --go_opt=Mhelloworld.proto=example.com/project/protos/fizz \
  ./proto/helloworld.proto

Note: The M before helloworld.proto

You need to add the path in the command or in the proto file

syntax = "proto3";

option go_package = "pkg/api";

this is the same for java, and python as well.

option java_package = "pkg/api";
option py_generic_services = "pkg/api";

As for the command

Makefile

PROJ_PATH=${CURDIR}

.PHONY: proto
proto: ## Generate protobuf code
# Compile proto files inside the project.
	protoc api.proto --proto_path=${PROJ_PATH}/proto --go_out=. --go-grpc_out=.