From 0fdd1e0c2a6e2895c13eda0f38afe5ecc96fe39d Mon Sep 17 00:00:00 2001
From: "Jakub A. W" <jakubwasek@gmail.com>
Date: Sat, 6 Dec 2025 23:12:01 +0100
Subject: [PATCH 1/3] chore: linter added + failover placeholder

---
 .golangci.yml                       | 11 ++++++++
 Makefile                            | 10 ++++++-
 README.md                           | 44 +++++++++++++++++++++++++++++
 cmd/gomodel/main.go                 |  1 +
 config/config.go                    |  3 +-
 config/failover.yaml                |  2 ++
 internal/core/interfaces.go         |  1 +
 internal/core/types.go              | 10 +++----
 internal/providers/openai/openai.go | 18 ++++++++----
 internal/server/handlers.go         | 10 +++++--
 internal/server/handlers_test.go    |  4 +--
 internal/server/http.go             |  1 -
 12 files changed, 98 insertions(+), 17 deletions(-)
 create mode 100644 .golangci.yml
 create mode 100644 config/failover.yaml

diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 00000000..e43999ec
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,11 @@
+run:
+  timeout: 5m
+
+linters:
+  enable:
+    - errcheck
+    - gosimple
+    - govet
+    - ineffassign
+    - staticcheck
+    - unused
diff --git a/Makefile b/Makefile
index 2af316c5..39c3b21e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: build run clean tidy test
+.PHONY: build run clean tidy test lint lint-fix
 
 # Build the application
 build:
@@ -20,3 +20,11 @@ tidy:
 test:
 	go test ./... -v
 
+# Run linter
+lint:
+	$(shell go env GOPATH)/bin/golangci-lint run ./...
+
+# Run linter with auto-fix
+lint-fix:
+	$(shell go env GOPATH)/bin/golangci-lint run --fix ./...
+
diff --git a/README.md b/README.md
index d20c2c72..dce9959a 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,50 @@ A high-performance LLM gateway written in Go.
      -d '{"model": "gpt-4o-mini", "messages": [{"role": "user", "content": "Hello!"}]}'
    ```
 
+## Development
+
+### Linting
+
+This project uses [golangci-lint](https://golangci-lint.run/) for code quality checks.
+
+#### Installation
+
+**macOS:**
+
+```bash
+brew install golangci-lint
+```
+
+**Linux:**
+
+```bash
+curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin
+```
+
+**Windows:**
+
+```bash
+go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+```
+
+For other installation methods, see the [official documentation](https://golangci-lint.run/welcome/install/).
+
+#### Usage
+
+Run the linter:
+
+```bash
+make lint
+```
+
+Run the linter with auto-fix:
+
+```bash
+make lint-fix
+```
+
+The linter configuration is defined in `.golangci.yml` and includes essential checks for code quality and correctness.
+
 ## Running with Docker
 
 You can use the official `golang:1.21-alpine` image to run the project in a container:
diff --git a/cmd/gomodel/main.go b/cmd/gomodel/main.go
index b6adb84c..fc6470c6 100644
--- a/cmd/gomodel/main.go
+++ b/cmd/gomodel/main.go
@@ -1,3 +1,4 @@
+// Package main is the entry point for the LLM gateway server.
 package main
 
 import (
diff --git a/config/config.go b/config/config.go
index 0b51569a..2527d3d7 100644
--- a/config/config.go
+++ b/config/config.go
@@ -1,3 +1,4 @@
+// Package config provides configuration management for the application.
 package config
 
 import (
@@ -33,7 +34,7 @@ func Load() (*Config, error) {
 	viper.SetDefault("server.port", "8088")
 
 	// Read config file (optional, won't fail if not found)
-	_ = viper.ReadInConfig()
+	_ = viper.ReadInConfig() //nolint:errcheck
 
 	// Environment variables override config file
 	viper.AutomaticEnv()
diff --git a/config/failover.yaml b/config/failover.yaml
new file mode 100644
index 00000000..0b4aaba3
--- /dev/null
+++ b/config/failover.yaml
@@ -0,0 +1,2 @@
+#failover:
+#  "gpt-5": [gemini3-pro, gemini2.5-pro]
diff --git a/internal/core/interfaces.go b/internal/core/interfaces.go
index a8df0ed5..79784036 100644
--- a/internal/core/interfaces.go
+++ b/internal/core/interfaces.go
@@ -1,3 +1,4 @@
+// Package core defines the core interfaces and types for the LLM gateway.
 package core
 
 import (
diff --git a/internal/core/types.go b/internal/core/types.go
index 55a8ab60..d522bc4d 100644
--- a/internal/core/types.go
+++ b/internal/core/types.go
@@ -2,10 +2,10 @@ package core
 
 // ChatRequest represents the incoming chat completion request
 type ChatRequest struct {
-	Model       string    `json:"model"`
-	Messages    []Message `json:"messages"`
 	Temperature *float64  `json:"temperature,omitempty"`
 	MaxTokens   *int      `json:"max_tokens,omitempty"`
+	Model       string    `json:"model"`
+	Messages    []Message `json:"messages"`
 	Stream      bool      `json:"stream,omitempty"`
 }
 
@@ -19,17 +19,17 @@ type Message struct {
 type ChatResponse struct {
 	ID      string   `json:"id"`
 	Object  string   `json:"object"`
-	Created int64    `json:"created"`
 	Model   string   `json:"model"`
 	Choices []Choice `json:"choices"`
 	Usage   Usage    `json:"usage"`
+	Created int64    `json:"created"`
 }
 
 // Choice represents a single completion choice
 type Choice struct {
-	Index        int     `json:"index"`
 	Message      Message `json:"message"`
 	FinishReason string  `json:"finish_reason"`
+	Index        int     `json:"index"`
 }
 
 // Usage represents token usage information
@@ -43,8 +43,8 @@ type Usage struct {
 type Model struct {
 	ID      string `json:"id"`
 	Object  string `json:"object"`
-	Created int64  `json:"created"`
 	OwnedBy string `json:"owned_by"`
+	Created int64  `json:"created"`
 }
 
 // ModelsResponse represents the response from the /v1/models endpoint
diff --git a/internal/providers/openai/openai.go b/internal/providers/openai/openai.go
index ac914e4a..4cf01620 100644
--- a/internal/providers/openai/openai.go
+++ b/internal/providers/openai/openai.go
@@ -1,3 +1,4 @@
+// Package openai provides OpenAI API integration for the LLM gateway.
 package openai
 
 import (
@@ -18,9 +19,9 @@ const (
 
 // Provider implements the core.Provider interface for OpenAI
 type Provider struct {
+	httpClient *http.Client
 	apiKey     string
 	baseURL    string
-	httpClient *http.Client
 }
 
 // New creates a new OpenAI provider
@@ -61,7 +62,9 @@ func (p *Provider) ChatCompletion(ctx context.Context, req *core.ChatRequest) (*
 	if err != nil {
 		return nil, fmt.Errorf("failed to send request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() {
+		_ = resp.Body.Close() //nolint:errcheck
+	}()
 
 	respBody, err := io.ReadAll(resp.Body)
 	if err != nil {
@@ -103,8 +106,11 @@ func (p *Provider) StreamChatCompletion(ctx context.Context, req *core.ChatReque
 	}
 
 	if resp.StatusCode != http.StatusOK {
-		respBody, _ := io.ReadAll(resp.Body)
-		resp.Body.Close()
+		respBody, err := io.ReadAll(resp.Body)
+		if err != nil {
+			respBody = []byte("failed to read error response")
+		}
+		_ = resp.Body.Close() //nolint:errcheck
 		return nil, fmt.Errorf("OpenAI API error (status %d): %s", resp.StatusCode, string(respBody))
 	}
 
@@ -124,7 +130,9 @@ func (p *Provider) ListModels(ctx context.Context) (*core.ModelsResponse, error)
 	if err != nil {
 		return nil, fmt.Errorf("failed to send request: %w", err)
 	}
-	defer resp.Body.Close()
+	defer func() {
+		_ = resp.Body.Close() //nolint:errcheck
+	}()
 
 	respBody, err := io.ReadAll(resp.Body)
 	if err != nil {
diff --git a/internal/server/handlers.go b/internal/server/handlers.go
index 512577c9..3cfa61f3 100644
--- a/internal/server/handlers.go
+++ b/internal/server/handlers.go
@@ -1,3 +1,4 @@
+// Package server provides HTTP handlers and server setup for the LLM gateway.
 package server
 
 import (
@@ -42,14 +43,19 @@ func (h *Handler) ChatCompletion(c echo.Context) error {
 		if err != nil {
 			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 		}
-		defer stream.Close()
+		defer func() {
+			_ = stream.Close() //nolint:errcheck
+		}()
 
 		c.Response().Header().Set("Content-Type", "text/event-stream")
 		c.Response().Header().Set("Cache-Control", "no-cache")
 		c.Response().Header().Set("Connection", "keep-alive")
 		c.Response().WriteHeader(http.StatusOK)
 
-		io.Copy(c.Response().Writer, stream)
+		if _, err := io.Copy(c.Response().Writer, stream); err != nil {
+			// Can't return error after headers are sent, log it
+			return nil
+		}
 		return nil
 	}
 
diff --git a/internal/server/handlers_test.go b/internal/server/handlers_test.go
index 1dfb4d33..ed02c01a 100644
--- a/internal/server/handlers_test.go
+++ b/internal/server/handlers_test.go
@@ -15,11 +15,11 @@ import (
 
 // mockProvider implements core.Provider for testing
 type mockProvider struct {
-	supportedModels []string
+	err             error
 	response        *core.ChatResponse
 	modelsResponse  *core.ModelsResponse
 	streamData      string
-	err             error
+	supportedModels []string
 }
 
 func (m *mockProvider) Supports(model string) bool {
diff --git a/internal/server/http.go b/internal/server/http.go
index d1feed42..64fae04c 100644
--- a/internal/server/http.go
+++ b/internal/server/http.go
@@ -39,4 +39,3 @@ func New(provider core.Provider) *Server {
 func (s *Server) Start(addr string) error {
 	return s.echo.Start(addr)
 }
-

From 62f82be15afe1e79d8fbbccba041b004c34b09cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20A=2E=20W=C4=85sek?= <jakubwasek@gmail.com>
Date: Sat, 6 Dec 2025 23:17:31 +0100
Subject: [PATCH 2/3] Update config/failover.yaml

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 config/failover.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/config/failover.yaml b/config/failover.yaml
index 0b4aaba3..23ee9d11 100644
--- a/config/failover.yaml
+++ b/config/failover.yaml
@@ -1,2 +1,2 @@
 #failover:
-#  "gpt-5": [gemini3-pro, gemini2.5-pro]
+#  "gpt-5": [gemini-1.5-pro, gemini2.5-pro]

From 64af9f95095787a5e494143b58815bf4a529d088 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20A=2E=20W=C4=85sek?= <jakubwasek@gmail.com>
Date: Sat, 6 Dec 2025 23:19:04 +0100
Subject: [PATCH 3/3] Update Makefile

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 39c3b21e..a0162c18 100644
--- a/Makefile
+++ b/Makefile
@@ -22,9 +22,9 @@ test:
 
 # Run linter
 lint:
-	$(shell go env GOPATH)/bin/golangci-lint run ./...
+	golangci-lint run ./...
 
 # Run linter with auto-fix
 lint-fix:
-	$(shell go env GOPATH)/bin/golangci-lint run --fix ./...
+	golangci-lint run --fix ./...