How to Import Proto Files from a Different Package Without Encountering the 'Missing Method Protoreflect' Error

In Go, protobufs are commonly used for data serialization. When organizing protobufs into different packages, it's possible to encounter an error related to the missing ProtoReflect method. This error occurs when trying to unmarshal data into a custom protobuf struct defined in a separate package.

To resolve this issue, ensure that the following steps are taken:

1. Ensure Consistent Protobuf Object Registration:

   In each package that uses custom protobuf structs, the corresponding *.pb.go file generated by protoc should be imported. This registers the protobuf structs with the ProtoReflect library, enabling seamless unmarshalling.

2. Verify Import Syntax:

   Check the import statements in the package where the unmarshalling is performed. Ensure that the import path matches either:

   • "github.com/golang/protobuf/proto"
   • "google.golang.org/protobuf/proto"

   Use the appropriate import path based on your existing dependencies.

Example:

Consider a project structure where protobuf files are defined in a separate package called prototemps.

ProjectFolder/
/prototemps/<all .proto and .pb.go exist here>  (Package "prototemps")
/reader/reader.go which fails when tries to do proto.Unmarshall (Package "reader")

To resolve the error in the reader package, ensure that the correct import statement is used:

package reader

import (
    "google.golang.org/protobuf/proto"
)

By following these steps, you can successfully import proto files from different packages and unmarshal data into your custom protobuf structs without encountering the 'missing method protoreflect' error.