I want to generate protobufs from proto files from cmd without using "option go_package "

I have to generate protobuf file from a proto file which import another proto file.
One another requirement, this has to be generated by cmd (by not defining "option go_package" in the proto file).

You can use the M flag to specify the go package. This is an example for how to execute the protoc command:

protoc -I=protos \
       --go_out=. \
       --go_opt=Mperson.proto=internal/pb \
       --go_opt=Maddressbook.proto=internal/pb \
       person.proto addressbook.proto

The directory structure for the above command is:

└── protos
    ├── addressbook.proto
    └── person.proto

protos/person.proto:

syntax = "proto3";

package example;

message Person {
  string name = 1;
  int32 id = 2;
  string email = 3;
}

protos/addressbook.proto:

syntax = "proto3";

package example;

import "person.proto";

message AddressBook {
  repeated Person people = 1;
}

And the final directory structure is:

├── internal
│   └── pb
│       ├── addressbook.pb.go
│       └── person.pb.go
└── protos
    ├── addressbook.proto
    └── person.proto

For complex use cases, it's recommended to use Buf. This answer shows how it can be used to generate code from complex proto files.

Let's say you have 3 files foo.proto, poo.proto and zoo.proto. The file foo.proto imports a message struct from poo.proto and zoo.proto. You need to write the command in a specific order which puts foo.proto(importing from other) first and poo.proto(giving import to other) and zoo.proto(giving import to other) after that.

Here is the command to generate protobufs without defining option go_package

protoc --proto_path=./ --go_out=./pb --go-grpc_out=./pb
--go_opt=Mfoo.proto=./ --go-grpc_opt=Mfoo.proto=./
--go_opt=Mpoo.proto=./ --go-grpc_opt=Mpoo.proto=./
--go_opt=Mzoo.proto=./ --go-grpc_opt=Mzoo.proto=./
foo.proto goo.proto zoo.proto

Notice the M before filename, it replaces option go_package in your code

foo.proto

syntax = "proto3";
import "goo.proto";
import "zoo.proto";

service Foo {
    rpc FooRPC(PooMessage) returns (ZooMessage) {}
}

poo.proto

syntax = "proto3";

message PooMessage {
    string body = 1;
}

zoo.proto

syntax = "proto3";

message ZooMessage {
    string body = 1;
}