[Go] generated API code swallows decoding errors

[kevinawoo]

Description

If the API returns a 200, but the JSON payload is malformed, then the code Go code generated hides the decoding errors. It's more useful to surface these errors to the developer to handle.

Generated template currently with 2.4.15:

if localVarHttpResponse.StatusCode < 300 {
	// If we succeed, return the data, otherwise pass on to decode error.
	err = a.client.decode(&localVarReturnValue, localVarBody, localVarHttpResponse.Header.Get("Content-Type"));
	if err == nil { 
		return localVarReturnValue, localVarHttpResponse, err
	}
}

Proposed change:

if localVarHttpResponse.StatusCode < 300 {
	// If we succeed, return the data, otherwise pass on to decode error.
	err = a.client.decode(&localVarReturnValue, localVarBody, localVarHttpResponse.Header.Get("Content-Type"));
	return localVarReturnValue, localVarHttpResponse, err
}

Swagger-codegen version

2.4.15.
Technically, it's not a regression since 2.3.x returned generic interface{}s. That version required you to do your own decoding.

Swagger declaration file content or url

not needed, it's with all Go generated code

Command line used for generation

swagger-cli generate

Steps to reproduce

You can generate any code.

Related issues/PRs

I opened #10429

Suggest a fix/enhancement

#10429