Presently, the Gateway requires an underlying implementation that supports the Federated specification. This is because Federation requires knowledge of entities to be able to query plan across multiple subgraphs (your Go server being one of those subgraphs). Other Go GraphQL projects (and many non-Go implementations!) do support Federation, like gqlgen, but otherwise it appears that the graphql-go project is tracking the feature request to add Federation support in this issue.
If there is exactly one service in your federated graph and it doesn’t support Federation, it’s plausible to believe that you could put the Apollo Gateway in front of it and it could work but that would not be a recommended configuration and it would probably require additional hoops to be jumped through.
Is it conceivable that you might be able to first transition to using gqlgen rather than graphql-go? That might be a good next step, though I’m not making any claims about the simplicity of doing so as I’m not familiar with the implementations in either one!