refactor: move backends into the backends directory (#1279)

* refactor: move backends into the backends directory

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* refactor: move main close to implementation for every backend

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

---------

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

backend/go/llm/transformers/gpt2.go

@@ -0,0 +1,42 @@
+package transformers
+
+// This is a wrapper to statisfy the GRPC service interface
+// It is meant to be used by the main executable that is the server for the specific backend type (falcon, gpt3, etc)
+import (
+	"fmt"
+
+	"github.com/go-skynet/LocalAI/pkg/grpc/base"
+	pb "github.com/go-skynet/LocalAI/pkg/grpc/proto"
+
+	transformers "github.com/go-skynet/go-ggml-transformers.cpp"
+)
+
+type GPT2 struct {
+	base.SingleThread
+
+	gpt2 *transformers.GPT2
+}
+
+func (llm *GPT2) Load(opts *pb.ModelOptions) error {
+	model, err := transformers.New(opts.ModelFile)
+	llm.gpt2 = model
+	return err
+}
+
+func (llm *GPT2) Predict(opts *pb.PredictOptions) (string, error) {
+	return llm.gpt2.Predict(opts.Prompt, buildPredictOptions(opts)...)
+}
+
+// fallback to Predict
+func (llm *GPT2) PredictStream(opts *pb.PredictOptions, results chan string) error {
+	go func() {
+		res, err := llm.gpt2.Predict(opts.Prompt, buildPredictOptions(opts)...)
+
+		if err != nil {
+			fmt.Println("err: ", err)
+		}
+		results <- res
+		close(results)
+	}()
+	return nil
+}