Adding Answer request AND adding best_of option to Completion. (#5)

* adding best of option

* adding answers option

* fixing small mistake

answers.go

@@ -0,0 +1,49 @@
+package gogpt
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"net/http"
+)
+
+type AnswerRequest struct {
+	Documents       [][]string `json:"documents"`
+	Question        string     `json:"question"`
+	SearchModel     string     `json:"search_model"`
+	Model           string     `json:"model"`
+	ExamplesContext string     `json:"examples_context"`
+	Examples        [][]string `json:"examples"`
+	MaxTokens       int        `json:"max_tokens"`
+	Stop            []string   `json:"stop"`
+}
+
+type AnswerResponse struct {
+	Answers           []string `json:"answers"`
+	Completion        string   `json:"completion"`
+	Model             string   `json:"model"`
+	Object            string   `json:"object"`
+	SearchModel       string   `json:"search_model"`
+	SelectedDocuments []struct {
+		Document int    `json:"document"`
+		Text     string `json:"text"`
+	} `json:"selected_documents"`
+}
+
+// Search — perform a semantic search api call over a list of documents.
+func (c *Client) Answers(ctx context.Context, request AnswerRequest) (response AnswerResponse, err error) {
+	var reqBytes []byte
+	reqBytes, err = json.Marshal(request)
+	if err != nil {
+		return
+	}
+
+	req, err := http.NewRequest("POST", c.fullURL("/answers"), bytes.NewBuffer(reqBytes))
+	if err != nil {
+		return
+	}
+
+	req = req.WithContext(ctx)
+	err = c.sendRequest(req, &response)
+	return
+}